This number is a prime.
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The largest known prime p equal to the digital length of a Mersenne prime, i.e., of the 21st Mersenne prime. Note that the order of this Mersenne prime, i.e., 21, followed by p and p followed by 21 are also primes, i.e., 212917 and 291721. [Loungrides]
The smallest of only two primes of form n^2 + 1 that is concatenated from two double-digit primes, i.e., 54^2+1 = 2917. (The other is 3137 = 56^2+1). [Loungrides]