Man Finds Largest Prime Number, And It's 23 Million Digits Long This past week, John Pace of Germantown, Tenn., made a massive discovery. He found the largest prime number known to humankind. It's more than 23 million digits long.

## A Tenn. Man Recently Discovered The Largest Prime Number Known To Humankind

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A Tenn. Man Recently Discovered The Largest Prime Number Known To Humankind

# A Tenn. Man Recently Discovered The Largest Prime Number Known To Humankind

## A Tenn. Man Recently Discovered The Largest Prime Number Known To Humankind

• `<iframe src="https://www.npr.org/player/embed/576301169/576301170" width="100%" height="290" frameborder="0" scrolling="no" title="NPR embedded audio player">`
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Illustration and Painting

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This past week, a FedEx employee from Germantown, Tenn., made a massive discovery — and it wasn't in any packages. John Pace found the largest prime number known to humankind.

And that number goes on to more than 23 million digits.

"So it's longer than anybody really wants to sit down and hear," he says.

If you're not great at math, here's a primer: Prime numbers can only be divided by 1 and themselves.

Pace found his prime as part of an online collective called the Great Internet Mersenne Prime Search, or GIMPS. Pace and thousands of volunteers ran software on their personal computers crunching numbers day-in and day-out.

Anyone can participate, you just need a computer, an internet connection and a lot of patience. Pace began his prime hunt 14 years ago.

"There was a \$100,000 prize attached to finding the first prime that had a 10 million digit result, and I was like, 'Well you know, I've got as much chance as anybody else,' " he says.

Pace's prime holds the title for the largest, but there are other bigger ones out there. And they're important, especially when it comes to cryptography, internet security and the future of computing.

"When they ultimately get to quantum computers, however long that takes, they'll be able to crack current encryption in milliseconds," Pace says. "So there's going to be a need for extremely large prime numbers, and I'd like to at least have left some legacy that I've helped contribute something to society."

NPR's Isabel Dobrin produced this story for the Web.