1931

This number is a prime.

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(1931 and 3119) is the only pair of 4-digit primes formed by concatenating in order and reverse order two consecutive primes in the sequence of odd-digit primes. [Loungrides]

The only prime concatenated from a pair of double-digit primes of form (n^2-6, n^2+6), where n is a prime. [Loungrides]

The largest of only three mountain primes each concatenated from two double-digit primes. The other two are 1361, 1741. [Loungrides]