PrimeGrid’sSierpinski/Riesel Base 5 Problem
On 4 December 2013 20:53:51 UTC, PrimeGrid's Sierpinski/Riesel Base 5 Problem project founda mega prime:
173198*51457792-1
The prime is 1,018,959 digits long and will enter Chris Caldwell's "The Largest Known Primes
Database" (http://primes.utm.edu/primes) ranked 67th overall. Incidentally, this is the first known
base 5 mega prime. 88 k's now remain in the Riesel Base 5 Problem.
The discovery was made by Motohiro Ohno of Japan using an Intel(R) Core(TM) i3-2120 CPU @3.30GHz with 4GB RAM running Microsoft Windows 7 Home Premium. This computer took
about 22 hours and 29 minutes to complete the primality test using LLR.
The prime was verified on 6 December 2013 5:27:38 UTC by Scott Brown of the United Statesusing an Intel(R) Core(TM) i7-2600 CPU @ 3.40GHz with 8 GB RAM running Microsoft Windows
7 Home Premium. This computer took about 33 hours and 22 minutes to complete the primality
test using LLR.
The credits for the discovery are as follows:

1. Motohiro Ohno (Japan), discoverer
2.
3.
4.

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=116553.
Using a single PC would have taken years to find this prime. So this timely discovery would nothave been possible without the thousands of volunteers who contributed their spare CPU cycles.
A special thanks to everyone who contributed their advice and/or computing power to the search especially all the sievers who work behind the scenes to make a find like this possible.
The Sierpinski/Riesel Base 5 Problem will continue to search for more primes. To join the searchplease visit PrimeGrid: http://www.primegrid.com

PrimeGrid’s
Sierpinski/Riesel Base 5 Problem
About PrimeGrid
PrimeGrid is a distributed computing project, developed by Rytis Slatkevičius, Lennart Vogel, andJohn Blazek, which utilizes BOINC and PRPNet to search for primes. PrimeGrid's primary goal isto bring the 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 of prime formsto search. With a little patience, you may find a large or even record breaking prime.
BOINC
The Berkeley Open Infrastructure for Network Computing (BOINC) is a software platform
for distributed computing using volunteered computer resources. It allows users toparticipate in multiple distributed computing projects through a single program. Currently
BOINC is being developed by a team based at the University of California, Berkeley led byDavid 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 specificallydesigned 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