On 20 June 2018, 06:35:42 UTC, PrimeGrid’s Sierpinski/Riesel Base 5 Problem project eliminated k=81556 by finding the mega prime:
The prime is 1,775,361 digits long and will enter Chris Caldwell's The Largest Known Primes Database ranked 61st overall. 32 k's now remain in the Sierpinski Base 5 Problem.
The discovery was made by Jiří Bočan (boceli) of the Czech Republic using an Intel(R) Core(TM) i3-6100 CPU @ 3.70GHz with 4 GB RAM running Microsoft Windows 7 Professional Edition. This computer took about 4 hours 23 minutes to complete the primality test using multithreaded LLR. Jiří is a member of the Czech National Team.
The prime was verified on 21 June 2018, 11:41:42 UTC by Wolfgang Schwieger (DeleteNull) of Germany using an Intel(R) Core(TM) i7-7820X CPU @ 3.60GHz with 32 GB RAM running Microsoft Windows 10 Professional Edition. This computer took about 1 hour 11 minutes to complete the primality test using multithreaded LLR. Wolfgang is a member of the SETI.Germany team.
For more details, please see the official announcement.