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

NPR: A Tenn. Man Recently Discovered The Largest Prime Number Known To Humankind. “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.”