1531

This number is a prime.

The smallest prime number that is a sum of distinct primes beginning and ending with the digit seven (7 + 727 + 797). [Capelle]

(1531, 1543, 1549) is the first case of three consecutive primes (q, r, s), such that (q^3+r^3+s^3)/3 is prime. [Loungrides]

The smallest prime p such that 2p-1, 3p-2, 4p-3 are prime. [Loungrides]

The distance in miles "as the crow flies" between Moscow and Tehran. [Kalantar]