# 112131323

This number is a prime.

The prime 112131323 is the concatenation of 1, 1, 2, 1, 3, 1, 3, 2, 3; which is the number of prime factors of Mersenne number M(n) = 2^n - 1 from n = 2 to n = 10 (counted with multiplicity), or from n+1 to 10 if we allow a left-most digit of 0. [Post]

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