According to CNN, the largest Mersenne prime number found to date has been verified: 230402457-1. It is 9,152,052 million digits long. It was found in mid-December after programming 700 computers years ago. The discovery is affiliated with the Great Internet Mersenne Prime Search, a global contest using volunteers who run software that searches for the largest Mersenne prime.
* Peter Montgomery was a co-worker of mine at SDC whose hobby was factoring Mersenne Primes using spare cycles on all of the BLACKER computers.