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 as
a Titan!
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.
- 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 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.
- Sophie Germain Prime Search: searching for primes p and 2p+1.
- The Riesel problem: helping to solve the Riesel Problem.
Recent Significant Primes
On 15 August 2018, 03:15:13 UTC, PrimeGrid's Sierpinski/Riesel Base 5 Problem project (SR5) eliminated k=194368 by finding the base 5 mega prime:
194368·52638045-1
The prime is 1,843,920 digits long and enters Chris Caldwell's The Largest Known Primes Database
ranked 1 st for base 5 primes and 60 th overall.
69 k's now remain in the Riesel Base 5 Problem.
The discovery was made by Honza Cholt ( Honza) of the Czech Republic
using an Intel(R) Core(TM) i7-8700K CPU @ 3.70GHz with 20 GB RAM running Microsoft Windows Server 2016.
This computer took about 4 hours and 44 minutes to complete the primality test using multithreaded LLR.
Honza is a member of the Czech National Team.
For more information, please see the Official Announcement.
On 4 August 2018, 09:10:53 UTC, PrimeGrid's Generalized Fermat Prime Search found the Generalized Fermat mega prime:
2312092524288+1
The prime is 3,336,572 digits long and enters Chris Caldwell's The Largest Known Primes Database
ranked 2 nd for Generalized Fermat primes and 24 th overall.
The discovery was made by Rob Gahan ( Robish) of Ireland
using an NVIDIA GeForce GTX 690 in an Intel(R) Core(TM) i7-3930K CPU at 3.20GHz with 12GB RAM, running Windows 10 Professional Edition.
This GPU took about 2 hours and 36 probable prime (PRP) test with GeneferOCL5.
Rob is a member of the Storm team.
The PRP was confirmed prime by an Intel(R) Core(TM) i7-7700K CPU @ 4.20GHz with 16GB RAM, running Microsoft Windows 10 Professional.
This computer took about 20 hours and 55 minutes to complete the primality test using multithreaded LLR.
For more information, please see the Official Announcement.
On 29 July 2018, 11:28:58 UTC, PrimeGrid's Sierpinski/Riesel Base 5 Problem project (SR5) eliminated k=66916 by finding the base 5 mega prime:
66916·52628609-1
The prime is 1,837,324 digits long and enters Chris Caldwell's The Largest Known Primes Database
ranked 1 st for base 5 primes and 61 st overall.
70 k's now remain in the Riesel Base 5 Problem.
The discovery was made by Honza Cholt ( Honza) of the Czech Republic
using an Intel(R) Core(TM) i7-8700K CPU @ 3.70GHz with 32 GB RAM running Microsoft Windows 10 Professional Edition.
This computer took about 4 hours and 35 minutes to complete the primality test using multithreaded LLR.
Honza is a member of the Czech National Team.
For more information, please see the Official Announcement.
Other significant primes
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News 
New SR5 Mega Prime!
On 15 August 2018, 03:15:13 UTC, PrimeGrid’s Sierpinski/Riesel Base 5 Problem project eliminated k=194368 by finding the mega prime:
194368*5^2638045-1
The prime is 1,843,920 digits long and will enter Chris Caldwell's The Largest Known Primes Database ranked 60th overall and is the largest known base 5 prime. 69 k's now remain in the Riesel Base 5 Problem.
The discovery was made by Honza Cholt (Honza) of the Czech Republic using an Intel(R) Core(TM) i7-8700K CPU @ 3.70GHz with 20 GB RAM running Microsoft Windows Server 2016. This computer took about 4 hours 44 minutes to complete the primality test using multithreaded LLR. Honza is a member of the Czech National Team.
The prime was verified on 17 August 2018, 10:15:20 UTC by Deano Montreuil (Deano Montreuil) of the United States using an Intel(R) Core(TM) i5-2400 CPU @ 3.10GHz with 8 GB RAM running Microsoft Windows 10 Core Edition. This computer took about 61 hours 55 minutes to complete the primality test using LLR. Deano is a member of the Aggie The Pew team.
For more details, please see the official announcement.
22 Aug 2018 | 13:51:16 UTC
· Comment
GFN-524288 Mega Prime!
On 4 August 2018, 09:10:53 UTC, PrimeGrid’s Generalized Fermat Prime Search found the Generalized Fermat mega prime:
2312092^524288+1
The prime is 3,336,572 digits long and enters Chris Caldwell's The Largest Known Primes Database ranked 2nd for Generalized Fermat primes and 24th overall.
The discovery was made by Rob Gahan (Robish) of Ireland using an NVIDIA GeForce GTX 690 in an Intel(R) Core(TM) i7-3930K CPU at 3.20GHz with 12GB RAM, running Windows 10 Professional Edition. This GPU took about 2 hours 36 minutes to probable prime (PRP) test with GeneferOCL5. Rob is a member of the Storm team.
The prime was verified on 4 August 2018, 23:28:14 UTC by Naoaki Tokuda (semanterion) of Japan using an NVIDIA Titan V in an Intel(R) Core(TM) i7-4960X CPU @ 3.60GHz with 64GB RAM, running Windows 7 Ultimate Edition. This GPU took about 24 minutes to probable prime (PRP) test with GeneferOCL5.
The PRP was confirmed prime by an Intel(R) Core(TM) i7-7700K CPU @ 4.20GHz with 16GB RAM, running Microsoft Windows 10 Professional. This computer took about 20 hours 55 minutes to complete the primality test using LLR.
For more details, please see the official announcement.
11 Aug 2018 | 13:08:34 UTC
· Comment
Yet Another SR5 Mega Prime!
On 29 July 2018, 11:28:58 UTC, PrimeGrid’s Sierpinski/Riesel Base 5 Problem project eliminated k=66916 by finding the mega prime:
66916*5^2628609-1
The prime is 1,837,324 digits long and will enter Chris Caldwell's The Largest Known Primes Database ranked 59th overall and is the largest known base 5 prime. 70 k's now remain in the Riesel Base 5 Problem.
The discovery was made by Honza Cholt (Honza) of the Czech Republic using an Intel(R) Core(TM) i7-8700K CPU @ 3.70GHz with 32 GB RAM running Microsoft Windows 10 Professional Edition. This computer took about 4 hours 35 minutes to complete the primality test using multithreaded LLR. Honza is a member of the Czech National Team.
The prime was verified on 29 July 2018, 15:45:07 UTC by James Krauss (Grebuloner) of the United States using an Intel(R) Core(TM) i7-7700K CPU @ 4.20GHz with 16 GB RAM running Microsoft Windows 10 Professional Edition. This computer took about 5 hours 38 minutes to complete the primality test using multithreaded LLR. James is a member of The Knights Who Say Ni! team.
For more details, please see the official announcement.
1 Aug 2018 | 14:12:44 UTC
· Comment
Another SR5 Mega Prime!
On 20 June 2018, 06:35:42 UTC, PrimeGrid’s Sierpinski/Riesel Base 5 Problem project eliminated k=81556 by finding the mega prime:
81556*5^2539960+1
The prime is 1,775,361 digits long and will enter Chris Caldwell's The Largest Known Primes Database ranked 61st overall. 32 k's now remain in the Sierpinski Base 5 Problem.
The discovery was made by Jiří Bočan (boceli) of the Czech Republic using an Intel(R) Core(TM) i3-6100 CPU @ 3.70GHz with 4 GB RAM running Microsoft Windows 7 Professional Edition. This computer took about 4 hours 23 minutes to complete the primality test using multithreaded LLR. Jiří is a member of the Czech National Team.
The prime was verified on 21 June 2018, 11:41:42 UTC by Wolfgang Schwieger (DeleteNull) of Germany using an Intel(R) Core(TM) i7-7820X CPU @ 3.60GHz with 32 GB RAM running Microsoft Windows 10 Professional Edition. This computer took about 1 hour 11 minutes to complete the primality test using multithreaded LLR. Wolfgang is a member of the SETI.Germany team.
For more details, please see the official announcement.
22 Jun 2018 | 18:40:05 UTC
· Comment
New SR5 Mega Prime!
On 19 June 2018, 09:48:29 UTC, PrimeGrid’s Sierpinski/Riesel Base 5 Problem project eliminated k=327926 by finding the mega prime:
327926*5^2542838-1
The prime is 1,777,374 digits long and will enter Chris Caldwell's The Largest Known Primes Database ranked 60th overall. 71 k's now remain in the Riesel Base 5 Problem.
The discovery was made by Selya Tsuji (stsuji) of Japan using an Intel(R) Core(TM) i7-6700K CPU @ 4.00GHz with 32 GB RAM running Microsoft Windows 10 Professional Edition. This computer took about 39 hours 37 minutes to complete the primality test using LLR. Selya is a member of Team 2ch.
For more details, please see the official announcement.
21 Jun 2018 | 19:03:11 UTC
· Comment
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Newly reported primes(Mega-primes are in bold.)
4099054380375*2^1290000-1 (MAGPIE); 4097108235657*2^1290000-1 (Travis); 599*2^3551793+1 (nilium); 100778678^32768+1 (SEARCHER); 100776958^32768+1 (Johny); 5605*2^1501702+1 (mattozan); 12851074^131072+1 (E. T. Drumm); 621*2^3551472+1 (Warp Zero); 6327*2^1501616+1 (Fudge); 6951*2^1501584+1 (usverg); 4095661713465*2^1290000-1 (usverg); 4093349878875*2^1290000-1 (Charles Handley); 100490012^32768+1 (Kellen); 100418806^32768+1 (Johny); 851*2^2656411+1 (Medijate); 5285*2^1501449+1 (usverg); 100250876^32768+1 (SEARCHER); 4093661636685*2^1290000-1 (Highlander_6596); 4091368039887*2^1290000-1 (4bc3); 100208254^32768+1 (Kellen) Last 24 hoursTop participants by work done in the last 24 hours | Top teams by work done in the last 24 hours |
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