467

This number is a prime.

467 is the only known Pennington "Gap" prime, i.e., a prime number of form (2^p-1)*(2^(p-1))-(2^q-1)*(2^(q-1))-1, where p, q (p>q) are two adjacent Mersenne exponents (p=5 and q=3). It equals the prime number of integers between two successive perfect numbers, namely 28 and 496. If another exists, it will have more than 100,000 decimal digits. [Honaker]