PrimeGrid’s321 Prime Search
On 23 June 2015 20:49:21 UTC, PrimeGrid’s 321 Prime Search found another
Mega Prime:
3*211895718-1
The prime is 3,580,969 digits long and will enter Chris Caldwell's “The Largest
Known Primes Database” (http://primes.utm.edu/primes) ranked 12th overall.
This is the largest known prime for the 3*2^n-1 form.
The discovery was made by Michael Schulz of Germany using an Intel(R)Core(TM) i5-4570 CPU @ 3.20GHz with 16 GB RAM running Darwin
14.3.0. This computer took about 9 hours and 57 minutes to complete theprimality test using LLR.
The prime was verified on 27 June 2015 3:56:03 UTC, by user Matthew of New
Zealand using an Intel(R) Core(TM) i7-4510U CPU @ 2.00GHz with 8 GB RAM
running Windows 7 Professional. This computer took about 33 hours and 40
minutes to complete the primality test using LLR.
Credits for the discovery are as follows:
1.
2.
3.
4.

Michael Schulz (Germany), discoverer
PrimeGrid, et al.
Srsieve, sieving program developed by Geoff Reynolds
LLR, primality program developed by Jean Penné

Entry in “The Largest Know Primes Database” can be found here:
http://primes.utm.edu/primes/page.php?id=120038
OpenPFGW, a primality program developed by Chris Nash & Jim Fougeron, wasused to check for Fermat Number divisibility (including generalized andextended). For more information about Fermat and generalized Fermat Number
divisors, please see Wilfrid Keller's sites:• http://www.prothsearch.net/fermat.html• http://www.prothsearch.net/GFNfacs.html
Using a single core PC would have taken decades to find this prime. So thistimely discovery would not have been possible without the thousands ofvolunteers who contributed their spare CPU cycles. A special thanks to everyone
who contributed their advice and/or computing power to the search.
The 321 Prime Search will continue to seek even larger primes. To join thesearch please visit PrimeGrid: http://www.primegrid.com

PrimeGrid’s
321 Prime Search
About PrimeGrid
PrimeGrid is a distributed computing project, developed by Rytis Slatkevičius,Lennart Vogel, and John Blazek, which utilizes BOINC and PRPNet to search forprimes. PrimeGrid's primary goal is to bring the excitement of prime finding to the"everyday" computer user. Simply download the software and let your computer
do the rest. Participants can choose from a variety of prime forms to search. Witha little patience, you may find a large or even record breaking prime.
BOINC
The Berkeley Open Infrastructure for Network Computing (BOINC) is asoftware platform for distributed computing using volunteered computerresources. It allows users to participate in multiple distributed computing
projects through a single program. Currently BOINC is being developed bya team based at the University of California, Berkeley led by David
Anderson.
This platform currently supports projects from biology to math to astronomy.
For more information, please visit BOINC: http://boinc.berkeley.edu
PRPNetPRPNet is a client/server application written by Mark Rodenkirch that is
specifically designed to help find prime numbers of various forms. It is easily
ported between various OS/hardware combinations. PRPNet does not run
each PRP test itself, but relies on helper programs, such as LLR, PFGW,
phrot, and genefer to do the work.
For more information, please visit PrimeGrid’s PRPNet forum thread:
http://www.primegrid.com/forum_thread.php?id=1215
For more information about PrimeGrid and a complete list of available prime
search projects, please visit: http://www.primegrid.com