On 20 January 2021, 11:58:27 UTC, PrimeGrid's 321 Search found the Mega Prime:
The prime is 5,063,112 digits long and enters Chris Caldwell's “The Largest Known Primes Database” ranked 21st overall.
The discovery was made by Rudi Tapper (ruditapper) of the United Kingdom using an AMD Ryzen Threadripper 3990X 64-Core Processor with 16GB RAM, running Microsoft Windows 10 Professional x64 Edition. This computer took about 5 hours, 40 minutes to complete the primality test using LLR2. Rudi Tapper is a member of the Antarctic Crunchers team.
For more details, please see the official announcement.