PrimeGrid’sSierpinski/Riesel Base 5 Problem
On 25 August 2017, 04:39:57 UTC, PrimeGrid’s Sierpinski/Riesel Base 5 Problem project
eliminated k=171362 by finding the mega prime:
171362*52400996-1

The prime is 1,678,230 digits long and will enter Chris Caldwell's “The Largest Known Primes
thDatabase” (http://primes.utm.edu/primes) ranked 57 overall. 73 k's now remain in the Riesel
Base 5 Problem.
The discovery was made by Frank Schwegler of the United States using an Intel(R) Core(TM)i7-5820K CPU @ 3.30GHz with 16GB RAM running Microsoft Windows 7 Ultimate Edition. This
computer took about 40 hours 12 minutes to complete the primality test using LLR.
The prime was verified on 26 August 2017 04:44:17 UTC by Sam Omlotek of the United Statesusing an Intel(R) Core(TM) i5-2500S CPU @ 2.70GHz with 8GB RAM, running macOS Sierra.
This computer took about 44 hours 35 minutes to complete the primality test using LLR. Sam isa member of the DONTPANIC team.
Credits for the discovery are as follows:
1.
2.
3.
4.

Frank Schwegler (United States), discoverer
PrimeGrid, et al.
Srsieve, sieving program developed by Geoff Reynolds
LLR, primality program developed by Jean Penné

Entry in “The Largest Known Primes Database” can be found here:
http://primes.utm.edu/primes/page.php?id=123866
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 CPUcycles. A special thanks to everyone who contributed their advice and/or computing power tothe search - especially all the sievers who work behind the scenes to make a find like thispossible.
The Sierpinski/Riesel Base 5 Problem will continue to search for more primes. To join thesearch please 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 and currently
administered by Iain Bethune, James Breslin, Scott Brown, Ulrich Fries, Charley Gielkens,Michael Goetz, Roger Karpin, Rytis Slatkevičius, and Van Zimmerman.
PrimeGrid is hosted by Rackspace, and their generous contributions have helped make thisproject possible.
PrimeGrid utilizes BOINC and PRPNet to search for primes with the primary goal of bringing theexcitement of prime finding to the "everyday" computer user. Simply download the software andlet your computer do the rest. 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.
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
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 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 onhelper programs, such as LLR, PFGW, phrot, wwww, 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