On 21 August 2017, 14:51:43 UTC, PrimeGrid’s Generalized Cullen/Woodall Prime Search found the largest known generalized Cullen prime:
Generalized Cullen numbers are of the form: n*b^n+1. Generalized Cullen numbers that are prime are called generalized Cullen primes. For more information, please see “Cullen prime” in The Prime Glossary.
The prime is 2,312,561 digits long and enters Chris Caldwell's The Largest Known Primes Database ranked 1st for Generalized Cullen primes and 30th overall.
The discovery was made by Hiroyuki Okazaki (zunewantan) of Japan using an Intel(R) CPU @ 2.90GHz with 16GB RAM, running Linux. This computer took about 12 hours and 39 minutes to complete the primality test using multithreaded LLR. Hiroyuki is a member of the Aggie The Pew team.
The prime was verified on 22 August 2017 17:24:17 UTC by user wuzzat of Australia using an Intel(R) Xeon(R) E5-2620 v3 CPU @ 2.40GHz with 256GB RAM, running Microsoft Windows Server 2008R2. This computer took about 31 hours 41 minutes to complete the primality test using LLR. Wuzzat is a member of the BOINC@AUSTRALIA team.
For more details, please see the official announcement.