PrimeGrid

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Digits	Prime Rank¹	App Types		Sub-Project	Available Tasks A² / B^3,4,5			UTC time	2025-10-09 19:04:42
7 106 698	19	CPU ^{MT F}		321 Prime Search (LLR)	1010	/	1000	User Count	356 724
3 149 923	170	CPU ^{MT F}		Compositorial Prime Search	1564	/	109K	Host Count	880 147
8 272 340	14	CPU ^{MT F}		Cullen Prime Search (LLR)	755	/	9434	Hosts Per User	2.47
8 605 137	14	CPU ^{MT F}		Extended Sierpinski Problem (LLR)	765	/	7335	Tasks in Progress	139 073
7 855 744	15	CPU ^{MT F}		Generalized Cullen/Woodall Prime Search (LLR)	759	/	1000	Primes Discovered	99 675
11 538 323	10	CPU ^{MT F}		Prime Sierpinski Problem (LLR)	407	/	9144	Primes Reported⁶ at T5K	37 282
4 287 008	73	CPU ^{MT F}		Primorial Prime Search	1512	/	5707	Mega Primes Discovered	2 896
1 139 197	1123	CPU ^{MT F}		Proth Prime Search (LLR)	1490	/	99K	TeraFLOPS	2 701.676
696 608	5K+	CPU ^{MT F}		Proth Prime Search Extended (LLR)	4007	/	746K
13 494 701	6	CPU ^{MT F}		Seventeen or Bust (LLR)	411	/	1699	PrimeGrid's 2025 Challenge Series World Bamboo Day Challenge Sep 18 08:00:00 to Sep 23 07:59:59 (UTC) Time until UNESCO Anniversary challenge: Days Hours Min Sec Standings World Bamboo Day Challenge (Compositorial): Individuals \| Teams
4 015 951	89	CPU ^{MT F}		Sierpinski / Riesel Base 5 Problem (LLR)	1510	/	132K
4 995 734	52	CPU ^{MT F}		The Riesel Problem (LLR)	1024	/	2000
7 716 691	16	CPU ^{MT F}		Woodall Prime Search (LLR)	776	/	9059
			GPU	Factorial / Compositorial (Sieve)	1991	/	∞
		CPU		Sierpinski / Riesel Base 5 Problem (Sieve)	980	/	∞

571 030	5K+	CPU ^{MT F}	GPU ^F	Generalized Fermat Prime Search (n=16)	1526	/	451K
1 122 136	1166	CPU ^{MT F}	GPU ^F	Generalized Fermat Prime Search (n=17 mega)	4962	/	114K
2 058 350	339	CPU ^{MT F}	GPU ^F	Generalized Fermat Prime Search (n=18)	1016	/	134K
3 794 527	98	CPU ^{MT F}	GPU ^F	Generalized Fermat Prime Search (n=19)	1001	/	17K
7 044 756	20	CPU ^{MT F}	GPU ^F	Generalized Fermat Prime Search (n=20)	1009	/	45K
13 424 175	6	CPU ^{MT4+ F}	GPU ^F	Generalized Fermat Prime Search (n=21)	423	/	14K
42 596 498	> 1 <		GPU ^F	Do You Feel Lucky? (n=23)	217	/	15K
		CPU ^MT	GPU	AP27 Search	1150	/	∞
¹ "Prime Rank" is where the leading edge candidate, if prime, would appear in the Top 5000 Primes list. "5K+" means the primes are too small to make the list. ² First "Available Tasks" number (A) is the number of tasks immediately available to send. ³ Second "Available Tasks" number (B) is additional candidates that have not yet been turned into workunits. If the first number (A) is 0, something is broken. If both numbers are 0, we've run out of work. ⁴ Underlined work is loaded manually. If the B number is not underlined, new candidates (B) are also automatically created from sieve files, which typically contain millions of candidates. If B is infinite (∞), there's essentially an unlimited amount of work available. ⁵ One or two tasks (A) are generated automatically from each candidate (B) when needed, so the total number of tasks available without manual intervention is either A+B or A+2*B. Normally two tasks are created for each candidate, however only 1 task is created if fast proof tasks are used, as designated by an ^"F" next to "CPU" or "GPU". ⁶ Includes all primes ever reported by PrimeGrid to Top 5000 Primes list. Many of these are no longer in the top 5000. ^F Uses fast proof tasks so no double check is necessary. Everyone is "first". ^MT Multithreading via web-based preferences is available. ^MT4+ Multithreading via web-based preferences is mandatory, requiring a minimum of 4 threads.

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 b^2ⁿ+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.

You can choose the projects you would like to run by going to the project preferences page.

World Bamboo Day Challenge
From September 18 08:00 to September 23 08:00 PrimeGrid will be running a 5 day challenge on the Compositorial project (to be started soon.)

For more information, please see this forum thread. 6 Sep 2025 | 7:48:03 UTC · Comment

William Rowan Hamilton's Birthday Challenge
Starting on August 4^th at 23:00:00 UTC, PrimeGrid will hold a 5 day challenge in the PPS (Proth Prime Search) project. Only tasks downloaded from the server after August 4^th at 23:00:00 UTC and returned to the server before August 9^th at 23:00:00 UTC will be counted for the challenge.

For more information and discussion about the challenge, please see https://www.primegrid.com/forum_thread.php?id=11959 30 Jul 2025 | 19:32:06 UTC · Comment

World Record Generalized Cullen Prime!
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 1^st 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. 26 Apr 2025 | 12:29:49 UTC · Comment

k=67612 Eliminated from SR5 Conjecture!
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 92^nd 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. 21 Apr 2025 | 1:21:14 UTC · Comment

GFN-19 Found!
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.
21 Apr 2025 | 0:55:57 UTC · Comment

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