PrimeGrid’s
Factorial Prime Search
On 30 August 2013, PrimeGrid’s PRPNet found the second largest known
Factorial prime:
147855!-1
The prime is 700,177 digits long and will enter Chris Caldwell's “The Largest
Known Primes Database” (http://primes.utm.edu/primes) ranked 2nd for
Factorial primes and 191st overall.
The discovery was made by Pietari Snow of Finland using an Intel(R) Core(TM)i7 CPU 940 @ 2.93GHz with 6 GB RAM running Linux. This computer took alittle over 69 hours and 37 minutes to complete the primality test using pfgw
x64. Pietari is a member of the PrimeSearchTeam.
Credits for the discovery are as follows:
1. Pietari Snow (Finland), discoverer
2. PrimeGrid, et al.
3. fsieve/psieve/fpsieve, sieve programs developed by Mark Rodenkirchand Geoff Reynolds
4. PFGW, primality program developed by Chris Nash & Jim Fougeron
Entry in “The Largest Know Primes Database” can be found here:
http://primes.utm.edu/primes/page.php?id=115328
This is only the 28th known Factorial prime...the 5th discovery in the last 9years. This is the first -1 Factorial prime since 103040!-1 was discovered inDecember 2010.
Using a single PC would have taken years to find this prime. So this timely
discovery would not have been possible without the hundreds of volunteers whocontributed their spare CPU cycles. A special thanks to everyone who offered
their advice and/or computing power to the search - especially Mark Rodenkirchand Geoff Reynolds who were major forces in moving the project forward. Also,
thank you to all the sievers and PRPNet’ers who contributed to this effort.
The Factorial Prime Search will continue to seek even larger primes. To join thesearch please visit PrimeGrid: http://www.primegrid.com

PrimeGrid’s
Factorial Prime Search
About PrimeGrid
PrimeGrid is a distributed computing project, developed by Rytis Slatkevičius, which
utilizes BOINC and PRPNet to search for primes. PrimeGrid's primary goal is to bringthe excitement of prime finding to the "everyday" computer user. Simply download thesoftware and let your computer do the rest. Participants can choose from a variety ofprime forms to search. With a little patience, you may find a large or even record
breaking prime.
BOINCThe Berkeley Open Infrastructure for Network Computing (BOINC) is a software
platform for distributed computing using volunteered computer resources. It
allows users to participate in multiple distributed computing projects through asingle program. Currently BOINC is being developed by a team based at theUniversity 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
PRPNet
PRPNet is a client/server application written by Mark Rodenkirch that isspecifically 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, andgenefer 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