The first Mersenne primes are 3, 7, 31, 127, etc. A Mersenne prime is a prime of the form 2P-1. For example, the number 10 is not prime because it is divisible by 2 and 5. The first prime numbers are 2, 3, 5, 7, 11, etc. An integer greater than one is called a prime number if its only divisors are one and itself. Prime numbers have long fascinated amateur and professional mathematicians. Mersenne numbers can be proved composite (not prime) by either finding a factor or by running a Lucas-Lehmer primality test. FPrime95 is a small and easy to use application that allows you to find Mersenne Prime numbers. Usually Prime95 will detect an error within a matter of minutes if an overclock is not stable, however many people like to let the system 'burn-in' overnight to ensure long-term stability. There are several options allowing the stress test to focus on the memory, processor, or a balance of both. Download Prime95 - a handy tool for overclockers and system stability checkers, Prime95 has a feature called 'Torture Test' that allows maximum stress testing on the CPU and RAM.