On 31 October 2016, 22:13:54 UTC, PrimeGrid’s Seventeen or Bust subproject found the Mega Prime:
The prime is 9,383,761 digits long and will enter Chris Caldwell's The Largest Known Primes Database ranked 7th overall.
This is the largest prime found attempting to solve the Sierpinski Problem and eliminates k=10223 as a possible Sierpinski number. It is also the largest known Proth prime, the largest known Colbert number, and the largest prime PrimeGrid has discovered. Among the 10 largest known prime numbers, it is the only prime that is not a Mersenne number, and the only known non-Mersenne prime over 4 million digits.
Until the Seventeen or Bust project shut down earlier in the year, this search was a collaboration between PrimeGrid and Seventeen or Bust. This discovery would not have been possible without all the work done over the years by Seventeen or Bust.
The discovery was made by Szabolcs Peter (SyP) of Hungary using an Intel(R) Core(TM) i7-4770 CPU @ 3.40GHz with 12GB RAM, running Windows 10 Enterprise Edition. This computer took about 8 days, 22 hours, 34 minutes to complete the primality test using LLR.
The prime was verified on 29 November 2016, 05:45:19 UTC by Heidi Kohne (Heidi1) of the United States using an AMD A6-3600 APU with 6GB RAM, running Microsoft Windows 7 Home Premium. This computer took about 27 days, 7 hours, 33 minutes to complete the primality test using LLR.
For more details, please see the official announcement.