PrimeGrid’s
Sierpiński/Riesel Base 5 Problem
On 26 April 2019, 13:27:42 UTC, PrimeGrid’s Sierpiński/Riesel Base 5 Problem project
eliminated k=138514 by finding the mega prime:138514*52771922+1
The prime is 1,937,496 digits long and enters Chris Caldwell's “The Largest Known
Primes Database” (https://primes.utm.edu/primes) ranked 63rd overall and is the largest
known base 5 prime. 31 k’s now remain in the Sierpiński Base 5 Problem.
The discovery was made by Ken Ito of Japan using an Intel(R) Core(TM) i9-9820X CPU@ 3.30GHz with 32 GB of RAM, running Microsoft Windows 10 Professional x64 Edition.
This computer took 2 hours and 46 minutes to complete the primality test using
multithreaded LLR. Ken is a member of Team 2ch.
The prime was verified on 27 April 2019, 07:28:26 UTC by Dmitry Domanov of Russia
using an Intel(R) Core(TM) i5-2310 CPU @ 2.90GHz with 3 GB of RAM, running
Microsoft Windows XP Professional x86 Edition. This computer took about 23 hours and24 minutes to complete the primality test using LLR. Dmitry is a member of the Russia
team.
The credits for the discovery are as follows:
1.
2.
3.
4.

Ken Ito (Japan), 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:
https://primes.utm.edu/primes/page.php?id=126425
Using a single PC would have taken years to find this prime. So this timely discovery
would not have been possible without the thousands of volunteers who contributed theirspare CPU cycles. A special thanks to everyone who contributed their advice and/or
computing power to the search -- especially to all the sievers who work behind thescenes to make a find like this possible.
PrimeGrid’s Sierpiński/Riesel Base 5 Problem will continue seeking primes for otherprimeless bases. To join the search please visit PrimeGrid: https://www.primegrid.com/

PrimeGrid’s
Sierpiński/Riesel Base 5 Problem
About PrimeGrid
PrimeGrid is a distributed computing project, developed by Rytis Slatkevičius andcurrently managed by James Breslin, Scott Brown, Ulrich Fries, Michael Goetz, RogerKarpin, Rytis Slatkevičius, and Van Zimmerman.
PrimeGrid utilizes BOINC and PRPNet to search for primes with the primary goal ofbringing 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 avariety of prime forms to search. With a little patience, you may find a large or evenrecord 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 to participate in multiple distributed computing projects through a single
program. Currently BOINC is being developed by a team based at the University ofCalifornia, Berkeley led by David Anderson.
This platform currently supports projects from biology to math to astronomy. For
more information, please visit BOINC: https://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, butrelies on helper programs, such as LLR, PFGW, phrot, wwww, and genefer to dothe work.
For more information, please visit PrimeGrid’s PRPNet forum thread:
https://www.primegrid.com/forum_thread.php?id=1215
For more information about PrimeGrid and a complete list of available prime search
projects, please visit: https://www.primegrid.com/