What is the largest known prime number? | iKnowledge

iknowledge.com — The largest known prime number is 243,112,609 − 1, a number with 12,978,189 digits. It tops off the Mersenne Primes, a group of the 47 known Mersenne prime numbers, and was discovered by Edson Smith at UCLA’s Mathematics Department on August 23,2008 as part of a project known as GIMPS (or Great Internet Mersenne Prime Search).