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 3 April 2018, 15:55:55 UTC, PrimeGrid's Extended Sierpinski Problem found the mega prime:
193997·211452891+1
The prime is 3,447,670 digits long and enters Chris Caldwell's The Largest Known Primes Database
ranked 23 rd overall.
This is the first k eliminated from the Extended Sierpinski Problem in over three years. 10 k's remain..
The discovery was made by Tom Greer ( tng*) of the United States
using an Intel(R) Xeon(R) E5-2620 v3 CPU @ 2.40GHz with 16GB RAM, running Microsoft Windows 10.
This computer took about 3 hours and 45 minutes to complete the primality test using multithreaded LLR.
Tom is a member of the Sicituradastra. team.
For more information, please see the Official Announcement.
On 21 March 2018, 22:13:39 UTC, PrimeGrid's Woodall Prime Search found the largest known Woodall prime:
17016602·217016602-1
The prime is 5,122,515 digits long and enters Chris Caldwell's The Largest Known Primes Database
ranked 1 st for Woodall primes and 16 th overall.
This is the 4 th largest prime found by PrimeGrid, the 4 th Woodall prime found by PrimeGrid, and the first Woodall prime found since December, 2007.
The discovery was made by Diego Bertolotti ( ScOrPIoN) of Italy
using an Intel(R) Core(TM) i7-2600 CPU at 3.40GHz with 8GB RAM, running Microsoft Windows 10.
This computer took about 4 days, 6 hours and 14 minutes to complete the primality test using LLR.
Diego is a member of the Boinc @ Italy team.
For more information, please see the Official Announcement.
On 20 March 2018, 08:28:32 UTC, PrimeGrid's Generalized Fermat Prime Search found the Generalized Fermat mega prime:
2061748524288+1
The prime is 3,310,478 digits long and enters Chris Caldwell's The Largest Known Primes Database
ranked 2 nd for Generalized Fermat primes and 22 nd overall.
The discovery was made by Cesare Marini ( Cesare Marini) of Italy
using an NVIDIA GeForce GTX 1060 in an Intel(R) Core(TM) i7-6700 CPU at 3.40GHz with 32GB RAM, running Windows 10 Professional Edition.
This GPU took about 1 hour and 32 minutes to complete the probable prime (PRP) test using GeneferOCL5.
The PRP was internally confirmed prime by PrimeGrid using an Intel(R) Core(TM) i7-7700K CPU @ 4.20GHz with 16GB RAM, running Microsoft Windows 10 Professional.
This computer took about 21 hours and 6 minutes to complete the primality test using multithreaded LLR.
For more information, please see the Official Announcement.
On 11 March 2018, 23:54:40 UTC, PrimeGrid's Generalized Cullen/Woodall Prime Search found the largest known Generalized Cullen prime:
1806676·411806676+1
The prime is 2,913,785 digits long and enters Chris Caldwell's The Largest Known Primes Database
ranked 1 st for Generalized Cullen primes and 27 th overall.
The discovery was made by Hiroyuki Okazaki ( zunewantan) of Japan
using an Intel(R) Xeon(R) E5-2670 CPU @ 2.60GHz with 4GB RAM, running Linux.
This computer took about 7 hours and 13 minutes to complete the primality test using multithreaded LLR.
Hiroyuki is a member of the Aggie The Pew team.
For more information, please see the Official Announcement.
Other significant primes
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News 
Do not use Nvidia driver 397.31
It has come to my attention that Nvidia recently released a new video driver that is causing widespread problems. 397.31 seems to cause the GPU to become inaccessible to both CUDA and OpenCL programs after a while, and can only be reset by rebooting the computer. It's likely this affects all BOINC projects and not just PrimeGrid. Indeed, it probably affects all GPU programs, even those that don't run under BOINC. There's a newer, hotfix driver 397.55 which seems to correct the problem. I strongly recommend either upgrading to 397.55 or rolling back to a driver earlier than 397.31.
More information can be found here.
6 May 2018 | 13:26:37 UTC
· Comment
New LLR apps
We have upgraded the version of LLR used on all of our LLR projects to LLR v.3.8.21.
As with the previous version of LLR, it is available in 32 and 64 bit versions for Windows and Linux, and 64 bits for Mac OS.
This release has two major features:
* Support for AVX/FMA3 on AMD Ryzen CPUs. You can expect about a 10% increase in speed on Ryzen processors as compared to earlier versions of LLR.
* A rare bug that sometimes caused errors when using multithreading has been corrected.
If you are using app_info.xml (aka anonymous platform) please upgrade to the latest LLR. The wrapper is unchanged. Upgrading is not mandatory, but is strongly recommended.
If you are not using app_info.xml, you will automatically get the new version with your next LLR task and no action is necessary on your part. If you're not sure if you're using app_info.xml you're almost certainly not using it, and no action is necessary.
17 Apr 2018 | 3:57:25 UTC
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ESP Mega Prime!
On 3 April 2018, 15:55:55 UTC, PrimeGrid’s Extended Sierpinski Problem Prime Search project found the Mega Prime:
193997*2^11452891+1
The prime is 3,447,670 digits long and will enter Chris Caldwell's The Largest Known Primes Database ranked 23th overall. This find eliminates k=193997; 10 k's remain in the Extended Sierpinski Problem.
The discovery was made by Tom Greer (tng*) of the United States using an Intel(R) Xeon(R) E5-2620 v3 CPU @ 2.40GHz with 16GB RAM, running Microsoft Windows 10. This computer took about 3 hours 45 minutes to complete the primality test using multithreaded LLR. Tom is a member of the Sicituradastra. team.
The prime was verified on 4 April 2018, 00:17:20 UTC by Gary Bauer (GDB) of the United States using an Intel(R) Core(TM) i7-8700K CPU @ 3.70GHz with 16GB RAM, running Microsoft Windows 10. This computer took about 2 hours 25 minutes to complete the primality test using multithreaded LLR.
For more details, please see the official announcement.
5 Apr 2018 | 20:35:05 UTC
· Comment
World Record Woodall Prime!
On 21 March 2018, 22:13:39 UTC, PrimeGrid’s Woodall Prime Search found the Woodall mega prime:
17016602*2^17016602-1
Woodall numbers are of the form: W(n)=n*2^n-1. Woodall numbers that are prime are called Woodall primes. For more information, please see “Woodall prime” in The Prime Glossary (http://primes.utm.edu/glossary).
The prime is 5,122,515 digits long and enters Chris Caldwell's The Largest Known Primes Database ranked 1st for Woodall primes and 16th overall. This is the 4th largest prime found by PrimeGrid, the 4th Woodall prime found by PrimeGrid, and the first Woodall prime found since December, 2007.
The discovery was made by Diego Bertolotti (ScOrPIoN) of Italy using an Intel(R) Core(TM) i7-2600 CPU at 3.40GHz with 8GB RAM, running Microsoft Windows 10. This computer took about 4 days 6 hours 14 minutes to complete the primality test. Diego is a member of the Boinc @ Italy team.
For more details, please see the official announcement.
1 Apr 2018 | 13:56:54 UTC
· Comment
GFN-524288 Mega Prime!
On 20 March 2018, 08:28:32 UTC, PrimeGrid’s Generalized Fermat Prime Search found the Generalized Fermat mega prime:
2061748^524288+1
The prime is 3,310,478 digits long and enters Chris Caldwell's The Largest Known Primes Database ranked 2nd for Generalized Fermat primes and 22nd overall.
The discovery was made by Cesare Marini (Cesare Marini) of Italy using an NVIDIA GeForce GTX 1060 in an Intel(R) Core(TM) i7-6700 CPU at 3.40GHz with 32GB RAM, running Windows 10 Professional Edition. This GPU took about 1 hour 32 minutes to probable prime (PRP) test with GeneferOCL5.
The prime was verified on 20 March 2018, 19:46:06 UTC by Håkan Lind (sangis43) of Sweden using an NVIDIA GeForce GTX 1070 in an Intel(R) Core(TM) i7-4930K CPU @ 3.40GHz with 16GB RAM, running Windows 7 Professional Edition. This GPU took about 1 hour 16 minutes to probable prime (PRP) test with GeneferOCL5. Håkan is a member of the Sicituradastra. 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 21 hours 6 minutes to complete the primality test using LLR.
For more details, please see the official announcement.
28 Mar 2018 | 11:45:28 UTC
· Comment
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