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.
- Fermat Divisor Search: a subset of the Proth Prime Search specificically searching for divisors of
Fermat numbers.
- 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.
- AP27 Search: searching for record length arithmetic progressions of primes.
Recent Significant Primes
On 17 February 2021, 14:27:08 UTC, PrimeGrid's Fermat Divisor Search found the Mega Prime
17·28636199+1
The prime is 2,599,757 digits long and enters Chris Caldwell's The Largest Known Primes Database
ranked 76 th overall.
The discovery was made by Tom Greer ( tng) of the United States using an Intel(R) Xeon(R) Gold 6140 CPU @ 2.30GHz with 1GB RAM, running Linux Ubuntu.
This computer took about 5 hours to complete the primality test using LLR2. Tom Greer is a member of the Antarctic Crunchers team.
For more information, please see the Official Announcement.
On 7 February 2021, 18:01:10 UTC, PrimeGrid's The Riesel Problem project eliminated k=9221 by finding the Mega Prime
9221·211392194-1
The prime is 3,429,397 digits long and enters Chris Caldwell's The Largest Known Primes Database
ranked 44 th overall. This is PrimeGrid's 17th elimination. 47 k's now remain.
The discovery was made by Barry Schnur ( BarryAZ) of the United States using an AMD Ryzen 5 2600 Six-Core Processor with 16GB RAM, running Microsoft Windows 10 Professional x64 Edition.
This computer took about 2 days, 29 minutes to complete the primality test using LLR2. Barry Schnur is a member of the BOINC Synergy team.
For more information, please see the Official Announcement.
On 1 February 2021, 11:26:31 UTC, PrimeGrid's 27121 Search through PRPNet found the Mega Prime
27·28342438-1
The prime is 2,511,326 digits long and enters Chris Caldwell's The Largest Known Primes Database
ranked 77 th overall.
The discovery was made by Andrew M. Farrow ( Nortech) of Australia using an Intel(R) Core(TM) i3-4170 CPU @ 3.70GHz with 4GB RAM, running Linux.
This computer took about 3 hours, 19 minutes to complete the primality test using LLR.
The prime was verified on 01 February 2021, 15:42:26 UTC, by an Intel(R) Core(TM) i7-8550U CPU @ 1.80GHz with 8 GB RAM, running Linux Manjaro. This computer took just under 2 hours 19 minutes to complete the primality test using LLR.
For more information, please see the Official Announcement.
Other significant primes
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News 
Yuri's Night Challenge starts April 11th
The third challenge of the 2021 Series will be a 3-day challenge celebrating the 60th anniversary of Yuri Gagarin's history-making venture into outer space. The challenge will be offered on the WW application, beginning 11 April 18:00 UTC and ending 14 April 18:00 UTC.
This is a relatively new subproject here at PrimeGrid, and there are currently no known Wall–Sun–Sun primes! You could be the first to find one!
To participate in the Challenge, please select only the Wieferich and Wall-Sun-Sun Prime Search (WW) project in your PrimeGrid preferences section.
Questions? Queries? Quips? Discuss on the forum thread for this challenge. Best of luck!
8 Apr 2021 | 15:32:42 UTC
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An Ending and a Beginning
This is the End...
Yesterday, the last task in our Fermat Divisor Search was sent out for processing. While there will likely be a few resends available over the next week or two, if you have PPS-DIV selected as your only project, we recommend choosing something else.
This project was very successful, having found two Fermat divisors! Congratulations everyone, and thank you for participating.
Discussion about the Fermat divisor search can be found here: https://www.primegrid.com/forum_forum.php?id=121
...And Also the Beginning
In less than an hour, at 12:00 UTC on Pi Day, our Sier"pi"nski's Birthday Challenge will be starting. This is a 10 day challenge on our Seventeen or Bust (SoB) project.
Details and discussion about the challenge can be found here: https://www.primegrid.com/forum_thread.php?id=9614
14 Mar 2021 | 11:23:58 UTC
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DIV Mega Prime!
On 17 February 2021, 14:27:08 UTC, PrimeGrid's Fermat Divisor Search found the Mega Prime:
17*2^8636199+1
The prime is 2,599,757 digits long and enters Chris Caldwell's “The Largest Known Primes Database” ranked 76th overall.
The discovery was made by Tom Greer (tng) of the United States using an Intel(R) Xeon(R) Gold 6140 CPU @ 2.30GHz with 1GB RAM, running Linux Ubuntu. This computer took about 5 hours to complete the primality test using LLR2. Tom Greer is a member of the Antarctic Crunchers team.
For more details, please see the official announcement.
3 Mar 2021 | 19:44:34 UTC
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TRP Mega Prime!
On 7 February 2021, 18:01:10 UTC, PrimeGrid’s The Riesel Problem project eliminated k=9221 by finding the mega prime:
9221*2^11392194-1
The prime is 3,429,397 digits long and will enter Chris Caldwell's The Largest Known Primes Database ranked 44th overall. This is PrimeGrid's 17th elimination. 47 k's now remain.
The discovery was made by Barry Schnur (BarryAZ) of the United States using an AMD Ryzen 5 2600 Six-Core Processor with 16GB RAM, running Microsoft Windows 10 Professional x64 Edition. This computer took about 2 days, 29 minutes to complete the primality test using LLR2. Barry Schnur is a member of the BOINC Synergy team.
For more details, please see the official announcement.
3 Mar 2021 | 19:38:29 UTC
· Comment
New 27 Mega Prime!
On 01 February 2021 UTC, PrimeGrid’s 27121 Prime Search, through PRPNet found the mega prime:
27*2^8342438-1
The prime is 2,511,326 digits long and will enter Chris Caldwell's The Largest Known Primes Database ranked 77th overall.
The discovery was made by Andrew M. Farrow (Nortech) of Australia using an Intel(R) Core(TM) i3-4170 CPU @ 3.70GHz with 4GB RAM, running Linux. This computer took just over 3 hours 19 minutes to complete the primality test using LLR.
The prime was verified on 01 February 2021, 15:42:26 UTC, by an Intel(R) Core(TM) i7-8550U CPU @ 1.80GHz with 8 GB RAM, running Linux Manjaro. This computer took just under 2 hours 19 minutes to complete the primality test using LLR.
For more details, please see the official announcement.
3 Mar 2021 | 19:32:41 UTC
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... more
News is available as an RSS feed 
Newly reported primes(Mega-primes are in bold.)
9613*2^1638624+1 (Homefarm); 7665*2^3365896+1 (Andrew Johnson); 125772166^65536+1 ([AF>EDLS]GuL); 237763668^32768+1 (WezH); 869*2^3030655+1 (Krzysiak_PL_GDA); 6175864545177*2^1290000-1 (Reggie); 237594028^32768+1 (WezH); 6173646025545*2^1290000-1 (vaughan); 237574496^32768+1 (ASomniphobeHere); 6173102164497*2^1290000-1 (JH30895); 8557*2^3365648+1 (KylePolansky); 643*2^3030650+1 (Penguin); 237539320^32768+1 (ASomniphobeHere); 6172586111655*2^1290000-1 (tng); 6675*2^1638474+1 (Randall J. Scalise); 237420230^32768+1 (Johny); 417*2^3029342+1 (288larsson); 237384588^32768+1 (Sean Tisdell); 6161755449087*2^1290000-1 (vaughan); 6163520994585*2^1290000-1 (JH30895) Top Crunchers:Top participants by RAC | Top teams by RAC |
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