# Browsing category prime numbers

## A Digital Root Puzzle

Every so often, a puzzle comes along and is just right for its time. Not so hard that you waste hours on it, but not so easy that it pops out straight away. I heard this from Simon at Big MathsJam last year and thought it'd be a good one

## From Euclid to Cantor

One of my favourite quotes is from Stefan Banach: "A good mathematician sees analogies between theorems. A great mathematician sees analogies between analogies." This post is clearly in the former camp. I'm fairly sure it's a trivial thing, but it's not something I'd noticed before. One of the first serious

## BREAKING NEWS: Largest prime discovered

39,916,801 has just been discovered to be the largest prime number. $11$ is a positive integer such that $11! + 1$ is prime; let $n = 11!$. Now, $n+2$ is clearly a multiple of 2, $n+3$ is a multiple of 3 and so on up to $2n$. Applying a similar

## Reverse engineering your prime birthday

If you follow the great big geeks on twitter - and , I'm looking at you - you'll have seen bits and pieces of discussion about prime birthdays. How to find your next prime birthday It's your prime birthday if you've been alive for a number of days that happens