1707

This number is a composite.

The first four nonzero digits of the sum of the series (1/64 + 1/729 + 1/15625 + 1/117649 + 1/1771561 + 1/4826809), i.e., the sum of the reciprocals of the sixth powers of the primes.

(2^1707-1)^2-2 is the first titanic Carol prime. (Note that Euler was born in 1707.) [Eller]