In the early 1950s, the largest known prime number had 44 digits—it now has more than 23 million

To a small but dedicated group of people, one question dominates their lives—when will we discover a one-billion digit prime?

A prime number is only divisible by one or itself (think 3, 5, 7, 11). Jonathan Pace had been searching for the largest prime for more than a decade until, at the end of last year, software on a computer the electrical engineer installed at his church in Tennessee unearthed a record-breaking 23,249,425-digit prime.

That number is 277,232,917-1.

Before the information age, some of the world’s smartest mathematicians could only prove that (2148+1)/17, a measly 44-digit number, was prime.

Year Largest prime Digits Prover
1588 2^17-1 6 Cataldi
1588 2^19-1 6 Cataldi
1772 2^31-1 10 Euler
1867 (2^59-1)/179951 13 Landry
1876 2^127-1 39 Lucas
1951 (2^148+1)/17 44 Ferrier

Then came computers, and the length of the largest known prime grew rapidly. However, we’re still a ways from a billion.

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