How Big Is the Largest Prime Number?

A prime number can only be divided evenly by one or by itself. For centuries, the calculation of prime numbers was a purely mathematical endeavor, but in the 19th century, especially during times of war, prime numbers were used to encode messages. Today, they’re used primarily in computer encryption. The newest prime number, discovered in December 2017 by electrical engineer and math enthusiast John Pace of Germantown, Tennessee, is known as M77232917 and has more than 23 million digits.

2, 3, 5, 7, 11, 13, 17, 19 and counting:

• M77232917 was discovered on Pace's personal computer. He has been searching for massive prime numbers for 14 years.
• Pace is a volunteer with the Great Internet Mersenne Prime Search, or GIMPS for short, a project started in 1996 and named after 17th-century French monk Marin Mersenne. Mersenne primes are found by continuously multiplying together twos, and then taking away one.
• The number is the 50th Mersenne prime to be discovered, and the 16th to be found using GIMPS software. M77232917 is about a million digits longer than the last prime discovery, made in 2016.