On 6 March 2016, 07:54:42 UTC, PrimeGrid’s Sierpinski/Riesel Base 5 Problem project eliminated k=77072 by finding the mega prime:
The prime is 1,495,746 digits long and enters Chris Caldwell's The Largest Known Primes Database ranked 53rd overall. This is the largest known base 5 mega prime. 34 k's now remain in the Sierpinski Base 5 Problem.
The discovery was made by Wolfgang Becker (flex) of Germany using an Intel(R) Core(TM)2 Duo CPU E8500 @ 3.16GHz with 4GB RAM running Windows 10 Professional. This computer took about 10 hours 42 minutes to complete the primality test using LLR. Wolfgang is a member of the BOINC@Heidelberg team.
The prime was verified on 9 March 2016, 22:19:31 UTC by Magnus Karlsteen (pep) of Sweden using an Intel(R) Xeon(R) CPU X5690 @ 3.47GHz with 24GB RAM running Windows 7 Professional. This computer took about 9 hours 9 minutes to complete the primality test using LLR.
For more details, please see the official announcement.