The book is now available! 2347
(another Prime Pages' Curiosity)
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+ 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]

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