On 19 Nov 2011 14:03:58, PrimeGrid's PRPNet found the largest known Generalized Fermat mega prime: 75898^524288+1
The prime is 2,558,647 digits long and enters Chris Caldwell's The Largest Known Primes Database ranked 1st for Generalized Fermat Primes and 13th overall. This is the first prime found at N=524288.
The discovery was made by Michael Goetz of the United States using an NVIDIA GeForce GTX 460 in an Intel Core2 Q6600 @ 2.4GHz system with 8GB RAM, running 64 bit Windows 7. The GPU took just under 5 hours to probable prime (PRP) test with GeneferCUDA. The CPU completed the primality test using pfgw64 in a little over 8 days! Michael is a member of the SETI.USA team.
For more details, please see the official announcement.