Unsolved Problems
- 2
- A-Sequence
- abc Conjecture
- Abelianity Conjecture
- Abhyankar-Sathaye Conjecture
- Ablowitz-Ramani-Segur Conjecture
- Affine Bernstein Conjecture
- Agoh's Conjecture
- Algebraic Period
- Aliquot Sequence
- Almost Perfect Number
- Alon-Tarsi Conjecture
- Alperin Weight Conjecture
- Alternating Series
- Andrica's Conjecture
- Anticanonical Nonvanishing Conjecture
- Apex Graph
- Arnold Conjecture
- Artin's Conjecture
- Artin K(pi,1) Conjecture
- Aspiring Number
- b-Semiampleness Conjecture
- Baillie-PSW Primality Test
- Ball-Evans Approximation Problem
- Ball Triangle Picking
- Banach's Simple Lebesgue Spectrum Problem
- Barker Code
- Barnette's Conjecture
- Baum-Connes Conjecture
- Baxter-Hickerson Function
- Beal's Conjecture
- Bell Number
- Benson's Formula
- Berge Perfect Matching Conjecture
- Berkovich-Dhar Conjecture
- Bermond-Thomassen Conjecture
- Berry Conjecture
- BFSS Model
- Bicentralizer
- Bifinite Correspondence
- Blaschke-Lebesgue Problem
- Bloch Conjecture
- Blocking Set
- Bochner-Riesz Conjecture
- Bogomolov-Pop Conjecture
- Borcea Variance Conjecture
- Borel Conjecture
- Borwein Conjectures
- Bounded Klt Complement Conjecture
- Bouniakowsky Conjecture
- Brannen's Conjecture
- Bras-Amorós Conjecture
- Braun's Conjecture
- Brocard's Conjecture
- Brocard's Problem
- Calderón's Inverse Problem
- Campana-Peternell Conjecture
- Cannon Conjecture
- Canonical Nonvanishing Conjecture
- Carmichael's Totient Function Conjecture
- Catalan's Aliquot Sequence Conjecture
- Central Binomial Coefficient
- Central Trinomial Coefficient
- Charged Penrose Inequality
- Chromatic Splitting Conjecture
- City-Building Sequence
- Class Number
- Clunie-Sheil-Small Conjecture
- Cluster Prime
- Coarse Novikov Conjecture
- Cocktail Party Graph
- Coin Problem
- Colin de Verdière Chromatic Conjecture
- Collatz Conjecture
- Colossally Abundant Number
- Combinatorial Invariance Conjecture
- Complementary Subspace Problem
- Completely Positive Matrix
- Complex Cobordism
- Concurrent Normals Conjecture
- Conference Graph
- Consecutive Prime Bias
- Constant Problem
- Continuous Core
- Conway's Refinement Conjecture
- Conway Thrackle Conjecture
- Costas Array
- Cotype-Cotype Problem
- Cramér Conjecture
- Cramér-Granville Conjecture
- Cube 3-Compound
- Cube-Full Number
- Cube Triangle Picking
- Cubic Nonhamiltonian Graph
- Curtis Conjecture
- Cycle Double Cover Conjecture
- Cyclic Number
- Darboux Map
- Dark Satanic Mills on a Cloudy Day
- David-Semmes Problem
- Daykin-Frankl Conjecture
- de Giorgi Conjecture
- de Grey Graphs
- de Polignac's Conjecture
- Dean's Conjecture
- Degree-Diameter Problem
- Deletable Prime
- Deligne-Drinfeld Conjecture
- Determined by Spectrum
- Disk Embedding Conjecture
- Disk Triangle Picking
- Dixmier Conjecture
- Dixmier Unitarizability Problem
- Domination Root
- Donaldson Tamed-to-Compatible Conjecture
- Donovan Conjecture
- Double-Cap Conjecture
- Double Mersenne Number
- Dynamical Uniform Boundedness Conjecture
- Earth-Moon Problem
- Eberhart's Conjecture
- Eden's Conjecture
- Edge-Graceful Graph
- Eilenberg-Ganea Conjecture
- Eisenbud-Green-Harris Conjecture
- l^1-Bass Conjecture
- Elliott-Halberstam Conjecture
- Elliptic Curve Rank
- Entanglement Area Law
- Entropy Conjecture
- Entropy Photon-Number Inequality
- Enumerative Chromatic Choosability
- Erdős Distinct Subset Sums Problem
- Erdős-Gyárfás Balanced Coloring Conjecture
- Erdős-Gyárfás Conjecture
- Erdős-Hajnal Conjecture
- Erdős-Ivić Conjecture
- Erdős Similarity Conjecture
- Erdős-Straus Conjecture
- Erdős-Turán Conjecture
- Erdős Unit Distance Problem
- Eternity
- Euclid-Mullin Sequence
- Euclidean Ramsey Theory
- Euler's Conjecture
- Euler-Mascheroni Constant
- Euler's Sum of Powers Conjecture
- Exponential Integral
- Extended Goldbach Conjecture
- Extended Trace Cone
- Factor Fundamental Group
- Factorial Square Product
- Factorial Sums
- Falconer Distance Conjecture
- Feit-Thompson Conjecture
- Fermat-Catalan Conjecture
- Finite Lattice Representation Problem
- Finitistic Dimension
- Fixed Price Problem
- Flint Hills Series
- Fontaine-Mazur Conjecture
- Forbidden Minor
- Fortunate Prime
- Foulkes Conjecture
- Four Exponentials Conjecture
- Fourier Restriction Conjecture
- Free Entropy Equality Problem
- Friendly Number
- Friendly Pair
- Fuglede's Conjecture
- Fujita Freeness Conjecture
- Fulkerson Conjecture
- Full Reptend Prime
- Gasoline Problem
- Generalized Abundance Conjecture
- Generalized Hodge Conjecture
- Generalized Hypergraph 4-Cycle
- Generalized Moore Graph
- Generalized Mukai Conjecture
- Generalized Riemann Hypothesis
- Geometric Langlands Correspondence
- Gepner-Type Stability Condition
- Gersten Conjecture
- Gilbreath's Conjecture
- Giuga's Conjecture
- Global Spherical Shell Conjecture
- Glushkov's L/X Problem
- Goldbach Conjecture
- Goldbach Partition
- Golomb Ruler
- Gömböc
- Gopalan-Servedio Conjecture
- Graceful Tree Conjecture
- Graph Crossing Number
- Graph Dimension
- Graph Distance Matrix
- Graph Reconstruction Conjecture
- Graph Spectrum
- Graph Toughness
- Grimm's Conjecture
- Grothendieck Homotopy Hypothesis
- Group-Ring Determinant Conjecture
- Guy's Conjecture
- H^*-Connected Graph
- Hadamard Conjecture
- Hadamard Matrix
- Hadwiger Conjecture
- Hadwiger-Nelson Problem
- Haemers Conjecture
- Hahn-Wilson Conjecture
- Haldane Conjecture
- Halin Snark
- Hamilton-Connected Graph
- Hamilton-Laceable Graph
- Happy End Problem
- Harborth Graph
- Hard Square Entropy Constant
- Hardy-Littlewood Conjectures
- Harmonic Dimension Comparison Conjecture
- Hasse's Conjecture
- He-Schramm Conjecture
- Heilbronn Triangle Problem
- Hénon-Lane-Emden Conjecture
- Hessian Conjecture
- Heule Graphs
- Hikita Conjecture
- Hilbert's Problems
- Hilbert-Smith Conjecture
- Hilbert's Tenth Problem
- Hilbert Transform Along a Vector Field
- Hodge Conjecture
- Hoffman-Singleton Theorem
- Hofstadter's Q-Sequence
- Holomorphic Cancellation Problem
- Holyhedron
- Home Prime
- Hot Spots Conjecture
- Hovey-Strickland Conjecture
- Howie Conjecture
- Hyperbolic Penrose Inequality
- Hypercube Graph
- Hypercube Point Picking
- Hyperinvariant Subspace Problem
- Hypersymplectic Deformation Conjecture
- Ibragimov-Iosifescu Conjecture
- Idoneal Number
- Iitaka Conjecture
- Integers with Restricted Digits
- Invariant Subspace Problem
- Ionization Conjecture
- Isomorphic Factorization
- Jacobian Conjecture
- Jiang-Su Stability
- Juggler Sequence
- Jumping Champion
- k-Server Problem
- k-Tuple Conjecture
- Kadison-Kaplansky Conjecture
- Kadison-Kastler Conjecture
- Kadison-Ringrose Cohomology Conjecture
- Kajitani-Ueno-Miyano Conjecture
- Kakeya Maximal Conjecture
- Kalai's 3^d Conjecture
- Kalai Flag Conjecture
- Kaplan-Yorke Conjecture
- Kaplansky Direct-Finiteness Conjecture
- Kaplansky's Quasitrace Conjecture
- Kaplansky Zero-Divisor Conjecture
- Kerr-Newman Penrose Inequality
- Kervaire Conjecture
- Khinchin's Constant
- Kimberling Sequence
- Kirchberg's Embedding Problem
- Klein Bottle Crossing Number
- Kobayashi Canonical-Ampleness Conjecture
- Kobon Triangle
- Kohn-Sham Representability
- Kollár-Pardon Conjecture
- Kosniowski Conjecture
- Kreisel Conjecture
- Krzyż Conjecture
- Kuga-Satake Correspondence
- Kuznetsov Rationality Conjecture
- Landau's Problems
- Lang-Plaut Problem
- Langlands Program
- Langton's Ant
- Latin Square
- Laughlin Spectral-Gap Conjecture
- Lech's Multiplicity Conjecture
- Lefschetz Standard Conjecture
- Legendre's Conjecture
- Lehmer's Mahler Measure Problem
- Lehmer's Totient Problem
- Levy's Conjecture
- Lex-Plus-Powers Conjecture
- Lieb-Thirring Inequality
- Lindelöf Hypothesis
- Linear Arboricity Conjecture
- Lipman-Zariski Conjecture
- Lipschitz Extension Problem
- Lipschitz Isomorphism Problem
- Littlewood Conjecture
- Local Density Conjecture
- Local Smoothing Conjecture
- Log Abundance Conjecture
- Log Gamma Function
- Lollipop Problem
- Lonely Runner Conjecture
- Lovász Conjecture
- Madelung Constants
- Magic Square
- Magic Square of Squares
- Mahler Volume Product Conjecture
- Mandelbrot Set
- Margulis-Platonov Conjecture
- Markov Type
- Markström Graph
- Mastermind
- Matroid Intersection
- Matthews Map
- McKean Entropy-Production Conjecture
- MDS Conjecture
- Mean Dimension
- Meissner Tetrahedra
- Merino-Welsh Conjecture
- Mersenne Prime
- Mertens Theorem
- Metric Entropy Duality Conjecture
- Metric Voting Distortion
- Millennium Prize Problems
- Milne's Rationality Conjecture
- Minimal Model Program
- Minimum Overlap Problem
- Minkowski-Bower Constant
- Minkowski Plane
- Minkowski's Question Mark Function
- Mixon Graphs
- Mondrian Art Problem
- Montgomery-Odlyzko Law
- Montgomery's Pair Correlation Conjecture
- Moore Parity Conjecture
- Morris's Conjecture
- Mortality Problem
- Mrs. Perkins's Quilt
- Mu-Constant Problem
- Multiplicative Complexity
- Multiplicative Persistence
- Mumford-Shah Conjecture
- Mutually Unbiased Bases
- Nagata-Biran-Szemberg Conjecture
- Nagata Conjecture
- Naimark's Problem
- Nearby Lagrangian Conjecture
- Net
- New Mersenne Prime Conjecture
- Newman's Conjecture
- No-Disentanglers Conjecture
- Nonhamiltonian Vertex-Transitive Graph
- Normal Number
- NP-Problem
- Nuclear Dimension
- Octahedral Number
- Odd Perfect Number
- Odd-Primary Kervaire Invariant Problem
- Operator Paving
- Orchard-Planting Problem
- Ordered Matrix Removal Conjecture
- Ore's Conjecture
- Orientable Genus
- Ostmann Conjecture
- p-adic Section Conjecture
- P=W Conjecture
- P Versus NP Problem
- Padé Conjecture
- Palindromic Number Conjecture
- Partition Function P Congruences
- Parts Graphs
- Path Complement Graph
- Peaceable Queens Problem
- Penrose Inequality
- Percolation Threshold
- Perfect Cuboid
- Perfect Gaussian Integer
- Perfect Magic Cube
- Perfect Matching Cover Index
- Perfect Number
- Permutation Class
- Petty's Projection-Volume Conjecture
- Pillai's Conjecture
- Pixton Completeness Conjecture
- Poisson Conjecture
- Pollock's Conjecture
- Pólya Eigenvalue Conjecture
- Pólya-Szegő Buckling Conjecture
- Pósa's Conjecture
- Powerful Number
- Prime Array
- Prime Gaps
- Prime Power Conjecture
- Projection Games Conjecture
- Projective Plane
- Propeller Conjecture
- Purely Infinite C^*-Algebra
- Quantum Geometric Langlands Correspondence
- Quantum Heisenberg Ferromagnet
- Quartic Nonhamiltonian Graph
- Quasi-Kernel
- Quasi-Riemann Hypothesis
- Quasiperfect Number
- Quillen Conjecture
- Quillen-Lichtenbaum Conjecture
- Quintic Nonhamiltonian Graph
- Rabin-Miller Strong Pseudoprime Test
- Radius of Comparison
- Random Close Packing
- Rational Distance Problem
- Rational Number
- Rectilinear Crossing Number
- Riemann Hypothesis
- Riemann Zeta Function
- Robin's Theorem
- Rokhlin's Multiple-Mixing Problem
- Rule 30 Prize Problems
- Ruth-Aaron Pair
- Ryser's Conjecture
- Sandglass Conjecture
- Sausage Conjecture
- Saxl Conjecture
- Schäffer's Conjecture
- Schanuel's Conjecture
- Schinzel's Hypothesis
- Schnell Fiber Space Conjecture
- Scholz Conjecture
- Schrödinger Pointwise Convergence Problem
- Schurian Graph
- Selfridge's Conjecture
- Separable Quotient Problem
- Serre's Intersection Multiplicity
- Seymour Conjecture
- Seymour's Second Neighborhood Conjecture
- Shafarevich Holomorphic Convexity Conjecture
- Shanks' Conjecture
- Shannon Capacity
- Shareshian-Wachs Conjecture
- Shephard's Conjecture
- Sidon Set
- Sidorenko's Conjecture
- Sierksma's Conjecture
- Sierpiński's Composite Number Theorem
- Sierpiński's Conjecture
- Sierpiński Number of the Second Kind
- Simon's L^2 Conjecture
- Simon's Problems
- Simonovits-Sós Conjecture
- Simplex Simplex Picking
- Singer Conjecture
- Skiving Stock Problem
- Skolem Problem
- Smale's Mean Value Conjecture
- Smale's Problems
- Small Cohen-Macaulay Module
- Smallest Cubic Crossing Number Graph
- Smallest Quartic Crossing Number Graph
- Smarandache Constants
- Smarandache Function
- Smarandache Prime
- Social Golfer Problem
- Solitary Number
- Solomon-Yau Least-Volume Conjecture
- Somos Sequence
- Sophie Germain Prime
- Sort-Then-Add Sequence
- Sous-Double
- Sous-Triple
- Sparse Ruler
- Sphere Packing
- Sphere Tetrahedron Picking
- Spherical Code
- Spider Graph
- Square Point Picking
- Stable Coordinate Conjecture
- Strict Comparison
- Strong Artin Conjecture
- Strong Cosmic Censorship
- Strong Hyper-Kähler SYZ Conjecture
- Strong Isotropic Constant Conjecture
- Strong Pseudoprime
- Strongly Regular Graph
- Sunflower
- Swinnerton-Dyer Conjecture
- Szpiro's Conjecture
- Tachikawa's Second Conjecture
- Tait's Knot Conjectures
- Tanc Function
- Tate Conjecture
- Taylor's Condition
- Tensor Square Conjecture
- Terao's Conjecture
- Termination of Flips Conjecture
- Ternary
- Tetrahedral Number
- Tetrahedron Circumscribing
- Tetrahedron Triangle Picking
- Thurston Elliptization Conjecture
- Toroidal Crossing Number
- Tóth-Varolin Conjecture
- Totient Function
- Totient Valence Function
- Tower of Hanoi
- Trautman Conjecture
- Traveling Salesman Problem
- Triangular Hilbert Transform
- Trilinear Hilbert Transform
- Trinomial Coefficient
- Turing Degree
- Tutte 4-Flow Conjecture
- Tutte Three-Edge-Coloring Conjecture
- Tuza's Conjecture
- Twin Prime Conjecture
- Twin Primes
- Twisted Group von Neumann Algebra
- Uchida's Homomorphism Conjecture
- Ultimate L Conjecture
- Unfolding
- Unibike Spiral
- Uniform Property Gamma
- Uniformity Conjecture
- Union-Closed Sets Conjecture
- Uniquely Pancyclic Graph
- Unistable Polyhedron
- Unitary Perfect Number
- Unitary Synthesis Problem
- Universal Turing Machine
- Unsolved Problems
- Untouchable Number
- van Cleemput-Zamfirescu Graphs
- Vinogradov's Least Primitive Root Conjecture
- Virasoro Conjecture
- Vizing Conjecture
- Vojta's Conjecture
- Wagstaff's Conjecture
- Wagstaff Prime
- Wall's D2 Problem
- Wall-Sun-Sun Prime
- Weak Inhomogeneous Duffin-Schaeffer Conjecture
- Weak Roberson Conjecture
- Weird Number
- Wichmann Ruler
- Wilson Prime
- Wolstenholme Prime
- Yang-Mills Existence and Mass Gap Problem
- Yau Nodal Set Conjecture
- Yau Uniformization Conjecture
- Z-Number
- Zarankiewicz's Conjecture
- Zariski Cancellation Problem
- Zariski Multiplicity Conjecture
- Zilber-Pink Conjecture
- Znám's Problem