807

This number is a composite.

807!/708! - 1 is prime. [Firoozbakht]

807 is the smallest proven coefficient k such that a) k*2^n+1 & k*2^n-1 are never twin primes; b) k*2^n-1 & k*2^(n+1)-1 are never Sophie Germain primes (personal communication from Wilfrid Keller, 20 April 2004). [Rivera]