717

This number is a composite.

A curious palindrome whose splitting up into parts 7 and 17 is interpretable in two ways. First as 'the 7th prime is 17' and secondly as 'the sum of the primes up to 7 is 17'. No larger palindrome is known having this two-fold property. [De Geest and Rosa]

The sum of the squares of the 717 consecutive primes starting from 1847 and 6959 is (in both cases) palindromic (18708380781 and 77817671877). [De Geest]

717 is the largest three-digit palindrome such that if it is raised to the sum of its digits plus the sum of its digits plus one, the result is prime. I.e., 717^(7+1+7)+(7+1+7)+1 is prime. [Opao]