2347

This number is a prime.

This prime is the concatenation of the Sophie Germain prime p=23 and the corresponding safe prime 2p+1. It is the largest such prime to have non-decreasing digits. [Hasler]

2347 and 4723 are the only primes concatenated from two double-digit primes whose the products of digits are perfect numbers, i.e., 6, 28. [Loungrides]

Breaking News: Beast Number (2366647) gets inside the mystery of numbers 23 and 47. [Lewicki]

The leading digits of the googol-th prime number. [Schmidt]