On 17 September 2017, 21:30:08 UTC, PrimeGrid’s Prime Sierpinski Problem project eliminated k=168451 by finding the mega prime:
The prime is 5,832,522 digits long and will enter Chris Caldwell's The Largest Known Primes Database ranked 13th overall. 9 k's now remain in the Prime Sierpinski Problem (2 of which are being searched as part of Seventeen or Bust). This is the third largest prime found by PrimeGrid.
Until the Prime Sierpinski Project shut down in 2014, this search was a collaboration between Primegrid and the Prime Sierpinski Project. This discovery would not have been possible without all the work done over the years by the Prime Sierpinski Project.
The discovery was made by Ben Maloney (paleseptember) of Australia using an Intel(R) Core(TM) i5-6400 CPU @ 2.70GHz with 16GB RAM running Windows 10 Professional Edition. This computer took about 2 days, 15 hours, 11 minutes to complete the primality test using LLR. Ben is a member of the Free-DC team.
The prime was verified on 23 September 2017 00:58:27 UTC by user cnoize using an Intel(R) Xeon(R) E5-2640 CPU @ 2.50GHz with 8GB RAM, running Windows Server 2008R2. This computer took about 6 days, 7 hours, 19 minutes to complete the primality test using LLR. Cnoize is a member of Team China, and the system was participating in the Gridcoin team.
For more details, please see the official announcement.