Double Mersenne Prime

A Double Mersenne Prime is a Mersenne Prime of the form 2p - 1 for which p is also a Mersenne Prime. There's currently only 4 known double Mersenne Primes: 7, 127, 2,147,483,647, and 170,141,183,460,469,231,731,687,303,715,884,105,727. It's conjectured that these are the only double Mersenne Primes in existence.
==See also==
Mersenne Primes
Category:Mersenne Primes
Category:Types of Primes
Category:Double Mersenne Primes