On 29 Oct 2011 11:31:47 UTC, PrimeGrid’s PRPNet found the largest known Generalized Fermat Prime: 361658^262144+1
The mega prime is 1,457,075 digits long and enters Chris Caldwell's The Largest Known Primes Database ranked 1st for Generalized Fermat Primes and 24th overall.
The discovery was made by Michel Johnson of Germany using an NVIDIA GeForce GTX 550 Ti in an AMD PHENOM II X6 1100T @ 3.3GHz system with 4GB RAM, running 32 bit Windows XP. This GPU took about 1 hour and 45 minutes to probable prime (PRP) test with GenefCUDA. (NOTE: This is the first prime found by geneferCUDA!) Michel is a member of the SETI.Germany team.
The prime was confirmed in 50 hours and 40 minutes using pfgw64 on an Intel Xeon 5410 @ 2.33GHz with 16GB RAM, running Windows Server 2003 x64.
For more details, please see the official announcement.