About
PrimeGrid's primary goal is to advance mathematics by enabling everyday computer users to contribute their system's processing power towards prime finding. By simply
downloading and installing BOINC and attaching to the PrimeGrid project,
participants can choose from a variety of prime forms to search. With a little patience, you may find a large or even record
breaking prime and enter into Chris Caldwell's The Largest Known Primes Database with a multi-million digit prime!
PrimeGrid's secondary goal is to provide relevant educational materials about primes. Additionally, we wish to contribute to the
field of mathematics.
Lastly, primes play a central role in the cryptographic systems which are used for computer security. Through the study of prime
numbers it can be shown how much processing is required to crack an encryption code and thus to determine whether current
security schemes are sufficiently secure. PrimeGrid is currently running several sub-projects:
- 321 Prime Search: searching for
mega primes of the form 3·2n±1.
- Cullen-Woodall Search: searching for
mega primes of forms n·2n+1 and
n·2n−1.
- Generalized Cullen-Woodall Search: searching for mega primes of forms n·bn+1 and
n·bn−1 where n + 2 > b.
- Extended Sierpinski Problem: helping solve the Extended Sierpinski Problem.
- Generalized Fermat Prime Search: searching for
megaprimes of the form b2n+1.
- Prime Sierpinski Project: helping the Prime Sierpinski Project solve the Prime Sierpinski Problem.
- Proth Prime Search: searching for primes of the form k·2n+1.
- Seventeen or Bust: helping to solve the Sierpinski Problem.
- Sierpinski/Riesel Base 5: helping to solve the Sierpinski/Riesel Base 5 Problem.
- The Riesel problem: helping to solve the Riesel Problem.
- AP27 Search: searching for record length arithmetic progressions of primes.
Recent Significant Primes
On 16 April 2025, 11:37:45 UTC, PrimeGrid's Generalized Cullen/Woodall PrimeSearch found the largest known Generalized Cullen Prime
4052186*694052186+1
The prime is 7,451,366 digits long and will enter 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 ( markfw) 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 information, 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*55501582+1
The prime is 3,845,446 digits long and will enter 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 information, please see the Official Announcement.
On 3 March 2025, 07:53:17 UTC, PrimeGrid's Generalized Fermat Prime Search found the Mega Prime
13427472524288+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 information, please see the Official Announcement.
Other significant primes
|
News 
Tour de Primes 2026
February is almost upon us, and with it, PrimeGrid's annual Tour de Primes.
This is a month long event where all can earn special Tour de Primes badges and a lucky few will win the coveted Tour de Primes jerseys.
More information can be found here.
26 Jan 2026 | 15:02:45 UTC
· Comment
World Nothing Day Challenge
From January 16 20:00 to January 23 20:00 PrimeGrid will be running a 7 day challenge on the Extended Sierpinski Problem (LLR) project.
For more information, please see this forum thread.
1 Jan 2026 | 5:11:57 UTC
· Comment
Winter Solstice Challenge
From December 21 15:03 to December 31 15:03 PrimeGrid will be running a 10 day challenge on the Generalized Fermat Prime Search n=22 project. Note the unusual start and end times!
For more information, please see this forum thread.
11 Dec 2025 | 15:08:14 UTC
· Comment
UNESCO Anniversary Challenge
From November 16 12:00 to November 23 12:00 PrimeGrid will be running a 7 day challenge on the Cullen Prime Search (LLR) and Woodall Prime Search (LLR) project.
For more information, please see this forum thread.
6 Nov 2025 | 15:19:48 UTC
· Comment
GFN-21 Prime Discovered; GFN-22 projected resumed
The first known GFN-21 prime has been discovered. More details will be released in the coming days. This is a 13 million digit prime that will enter the Top 5000 prime list as the 6th largest known prime.
With this discovery, our GFN-22 project has been restarted at b=400K. These numbers are 23 million digits in length.
14 Oct 2025 | 4:18:24 UTC
· Comment
... more
News is available as an RSS feed 
Newly reported primes(Mega-primes are in bold.)
429562606^131072+1 (Grebuloner); 999*2^4255666+1 (dawid); 4321*2^2343044+1 (Stony666); 429785684^131072+1 (Tyler); 429267826^131072+1 (w a h); 429320748^131072+1 (Michael Millerick); 429193154^131072+1 (Tamagoch); 9417*2^2342710+1 (Tazz); 428702274^131072+1 (cellarnoise2); 429172048^131072+1 (yuki); 617*2^4263387+1 (Margus); 753*2^4260184+1 (288larsson); 1089*2^4259323+1 ([AF>Le_Pommier] Aillas); 1011*2^4211111+1 (Buckeye4lf); 425560256^131072+1 (10esseeTony); 428412262^131072+1 (meso@Mayoineko); 426486542^131072+1 (pschoefer); 408718738^131072+1 (gu_wo); 427736228^131072+1 (William Byerly); 427363252^131072+1 (CavernDigger88) Top Crunchers:Top participants by RAC | Top teams by RAC |
| 
