On 21 October 2015, 05:23:34 UTC, PrimeGrid’s Sierpinski/Riesel Base 5 Problem project eliminated k=100186 by finding the mega prime:
The prime is 1,453,686 digits long and enters Chris Caldwell's The Largest Known Primes Database ranked 53rd overall. This is the largest known base 5 mega prime. 78 k's now remain in the Riesel Base 5 Problem.
The discovery was made by Toshitaka Kumagai (Toshitaka Kumagai) of Japan using an Intel(R) Xeon(R) CPU E3-1220 V2 @ 3.10GHz with 32GB RAM running Linux. This computer took about 15 hours 41 minutes to complete the primality test using LLR.
The prime was verified on 21 October 2015, 18:46:14 UTC by Scott Brown (Scott Brown) of the United States using an Intel(R) Core(TM) i7-4790 CPU @ 3.60GHz with 8GB RAM running Microsoft Windows 7 Enterprise. This computer took about 27 hours 36 minutes to complete the primality test using LLR. Scott is a member of the Duke University team.
For more details, please see the official announcement.