On 29 Jan 2012, 08:10:03 UTC, PrimeGrid’s PRPNet found the largest known generalized Cullen prime: 427194*113^427194+1
The prime is 877,069 digits long and enters Chris Caldwell's The Largest Known Primes Database ranked 1st for generalized Cullen primes and 57th overall.
The discovery was made by Ricky L. Hubbard (MiHost) of the United States using an AMD Phenom II X6 1090t @ 3.2GHz with 8GB RAM, running Windows 7. This computer took 7 hours and 15 minutes to complete the probable prime test using pfgw64 and 7 hours 20 minutes to complete the primality test again using pfgw64. Ricky is a member of the AMD Users Team.
For more details, please see the official announcement.