Yesterday, GIMPS found the 50th Mersenne prime, now the world’s largest known prime. It is 23,249,425 digits long, so it’s really very big indeed.

GIMPS, the Great Internet Mersenne Prime Search, is a sort of distributed computing project which allows ordinary people to pool together to look for really big primes. This one, , was found by Jonathan Pace, a 51 year old electrical engineer. It took about 6 days and was independently verified by 4 other people and programs. Pace was awarded $3,000 for finding the prime, though it’s worth mentioning that he’s been looking for primes for 14 years now, so I imagine his electricity costs were not inconsiderable.