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]
The leading digits of the googol-th prime number. [Schmidt]
(There are 3 curios for this number that have not yet been approved by an editor.)
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