For example, 7 is a prime number since I'm left with a remainder or a fractional component if I divide 7 by anything other than itself or 1. 6 is not a prime because I can divide 6 by 2 and get 3.

Grothendieck is said to have replied: “57.” Although it is hard to determine the truth of this story, 57 has since been known in nerd circles as the Grothendieck “prime number”—even ...

In this KS2 Maths article you’ll learn techniques to find out if a number is a prime number. We also have a KS2 Maths quiz and lots of examples.

For instance, the largest known prime number, which is 2 136279841 − 1, is 41,024,320 digits long. At first, that number may seem mind-bogglingly large.

If you do this with all numbers from 2 to 100, only prime numbers will remain. Sieving multiples of 2, 3, 5 and 7 leaves only the primes between 1 and 100. Courtesy of M.H. Weissman.