## prime number

*257,885,161-1*. This massive 17,425,170 digit number was discovered thanks to clever distributed computing software that uses idle computer time donated by volunteers.

**Julian Havil**looks at a little-known algorithm that sieves out all primes up to a given number, and which is astonishing in its simplicity.

**Abigail Kirk**investigates a method that does just that.

- Happy birthday Plus! — celebrating 10 years of bringing mathematics to life
- Plus 10 — what were the greatest mathematical advances in the last decade?

The Great Internet Mersenne Prime Search strikes again