A right-angled polytope is a convex polytope whose dihedral angles are all . In hyperbolic geometry,
reflections in its facets generate a discrete reflection group (Potyagailo and Vinberg
2005).
Guo and Zheng (2026) proved that every compact right-angled hyperbolic 4-polytope has at least 600 vertices, 1200 edges,
720 two-dimensional faces, and 120 facets, and has hyperbolic volume at least . Equality in any of these bounds
holds iff the polytope is isometric to the compact right-angled
hyperbolic 120-cell. The statement concerns the hyperbolic
realization, rather than the Euclidean regular polytope. Guo and Zheng (2026) report
AI assistance with the mathematical proof.