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Smarandache Prime


A Smarandache prime is a prime Smarandache number, obtained by concatenating the decimal representations of the first n positive integers for some n>=1. As of Oct. 2026, no Smarandache primes are known. Reported search limits are summarized in the table below. Batalov (2015b) extended the search from index 77000 to 200000 by Oct. 22, 2015. The subsequent distributed Great Smarandache PRPrime search reached index 344869 by Dec. 5, 2016. Batalov (2018) reported on Jun. 15, 2018 that no Smarandache primes occur through index 10^6. WraithX (2025) subsequently reported no probable primes through index 1200000 on Mar. 23, 2025.

Mayer (2015) gave a corrected heuristic estimate of about 1.13 primes among the first million terms. His model assigns an eligible term of size x the probability 15/(4lnx) of being prime, conditioning on its being relatively prime to 30. If the count is additionally modeled by a Poisson distribution with this expected count, the probability of finding no primes is approximately e^(-1.13) approx 0.32.

search limitreference
200Fleuren (1999)
38712E. Weisstein (Mar. 21, 2009)
64728E. Weisstein (Oct. 17, 2011)
77000M. Alekseyev (Oct. 3, 2015)
200000S. Batalov (Oct. 22, 2015)
344869The Great Smarandache PRPrime search (Dec. 5, 2016)
1000000S. Batalov (Jun. 15, 2018)
1200000WraithX (Mar. 23, 2025)

If initial digit prefixes ending inside the final integer are allowed (for example, ending after the 1 in 10), prime prefixes are known. In particular, such primes are Champernowne-constant primes, the first few of which are 1234567891, 12345678910111, ... (OEIS A176942), which have 10, 14, 24, 235, 2804, 4347, 37735, ... decimal digits (OEIS A071620).


See also

Consecutive Number Sequences, Integer Sequence Primes, Smarandache Number, Smarandache Sequences

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References

--. "The Great Smarandache PRPrime Search." http://smarandache.ddns.net:1200/server_stats.html.Batalov, S. "Smarandache Prime(s)." Oct. 5, 2015a. https://www.mersenneforum.org/node/15124#post15124.Batalov, S. Oct. 22, 2015b. https://www.mersenneforum.org/node/15124/page4#post556778.Batalov, S. Jun. 15, 2018. https://www.mersenneforum.org/node/15124/page4#post661563.Fleuren, M. "Smarandache Factors and Reverse Factors." Smarandache Notions J. 10, 5-38, 1999.Mayer, E. W. "Expected Number of Primes in OEIS A007908." Mersenne Forum, Oct. 17, 2015. https://www.mersenneforum.org/node/15131?p=556356#post556356.Sloane, N. J. A. Sequences A007908, A071620, and A176942 in "The On-Line Encyclopedia of Integer Sequences."WraithX. "Smarandache Prime(s?)." Mersenne Forum, Mar. 23, 2025. https://www.mersenneforum.org/node/15124?p=1072727#post1072727.

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Smarandache Prime

Cite this as:

Weisstein, Eric W. "Smarandache Prime." From MathWorld--A Wolfram Resource. https://mathworld.wolfram.com/SmarandachePrime.html

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