PrimeGrid

On 16 April 2025, 11:37:45 UTC, PrimeGrid's Generalized Cullen/Woodall PrimeSearch found the largest known Generalized Cullen Prime: 4052186 * 69 4052186 +1 Generalized Cullen numbers are of the form: n*bn+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 7,451,366 digits long and enters “The Largest Known Primes Database” ranked 1st for Generalized Cullen Primes and 16th overall. This is the second largest prime ever found by PrimeGrid. Base 69 was one of 9 primeless Generalized Cullen bases for b ≤121 that PrimeGrid is searching. The remaining bases are 13, 29, 47, 49, 55, 101, 109 & 121. The discovery was made by Mark Williams of the United States using 8 cores of an AMD EPYC 9554 64-Core Processor with 196GB RAM, running Microsoft Windows 10 Professional x64 Edition. This computer took about 10 hours, 15 minutes to complete the probable prime (PRP) test using PRST. Mark is a member of TeAm AnandTech. The PRP was confirmed prime on 17 April 2025 by an AMD Ryzen 9 7950X3D @ 4.20GHz with 128GB RAM, running Debian 12.5. This computer, using 8 cores, took 12 hours and 32 minutes to complete the primality test using PRST. For more details, please see the official announcement.

On 8 April 2025, 12:49:49 UTC, PrimeGrid’s Sierpiński/Riesel Base 5 Problem project eliminated k=67612 by finding the mega prime: 67612*5 5501582 +1 The prime is 3,845,446 digits long and enters “The Largest Known Primes Database” ranked 92nd overall. 27 k’s now remain in the Sierpiński Base 5 problem. The discovery was made by Kai Presler (Aperture_Science_Innovators) of Australia using 8 cores of an AMD Ryzen 9 7945HX with 14GB RAM, running Linux Mint 21.3. This computer took about 1 hour, 24 minutes to complete the probable prime (PRP) test using PRST. Kai is a member of team [H]ard|OCP. The PRP was confirmed prime on 8 April 2025, 20:19:10 UTC, by an AMD Ryzen 9 7950X3D @ 4.20GHz with 128GB RAM, running Debian 12.5. This computer, using 4 cores, took 3 hours and 44 minutes to complete the primality test using LLR2. For more details, please see the official announcement.

On 3 March 2025, 07:53:17 UTC, PrimeGrid's Generalized Fermat Prime Search found the Mega Prime: 13427472 524288 +1 The prime is 3,737,122 digits long and will enter “The Largest Known Primes Database” ranked 15th for Generalized Fermat primes and 94th overall. The discovery was made by Jean-Luc Garambois ([AF>Amis des Lapins] Jean-Luc) of France using an NVIDIA GeForce RTX 4080 SUPER in an AMD Ryzen Threadripper 3990X 64-Core Processor with 256GB RAM, running Linux Ubuntu 22.04.5 LTS. This computer took about 15 minutes and 23 seconds to complete the probable prime (PRP) test using Genefer22. Jean-Luc is a member of the L'Alliance Francophone team. The PRP was confirmed prime on 17 April 2025 by an AMD Ryzen 9 7950X3D @ 4.20GHz with 128GB RAM, running Debian 12.5. This computer took about 20 hours, 35 minutes to complete the primality test using LLR. For more details, please see the official announcement.