Mr. Pace’s discovery is known as M77232917 and was announced on Jan. 3. It is expressed as 277,232,917 – 1 and is 23,249,425 digits, nearly one million digits larger than the previous record-holder, which The New York Times wrote about in 2016. As we explained then:

A prime number is not divisible by any positive integer except 1 and itself. Some prime numbers are named after Marin Mersenne, a French theologian and mathematician who studied them in the early 17th century. They can be written in the form 2n – 1 where n is an integer. For example, 3 is a Mersenne prime. Plug in 2 for n, and you find 22 − 1 = 4 − 1 = 3. But not all integers plugged into this expression generate a prime number, and as integers get bigger, prime numbers become rarer.

To recruit hunters for them, a volunteer project called the Great Internet Mersenne Prime Search, or Gimps, came on the scene in 1996.

Mr. Pace said that when he became a Gimps volunteer, 14 years ago, he was excited by the idea of finding the first Mersenne prime with at least 10 million digits, and winning the $100,000 prize. But that discovery was made on a U.C.L.A. computer in 2008.

As the years went by, and other Mersenne prime numbers were found, Mr. Pace kept running the software in the background. “The C.P.U. will only work on it if there is literally nothing else for it to do,” he said. He started with computers at home and then used the ones at the Germantown Church of Christ, where he is a deacon and the network administrator.