Nobody has ever found an odd perfect number. So do they exist at all and, if yes, what do they look like?

Perfect numbers have foxed mathematicians for over 2000 years. Here's a quick look at the long struggle to find them.

A new prime number with nearly 25 million digits was discovered just in time for Christmas.

Of numbers, beauty and bizarre animals.

Number theory is famous for problems that everyone can understand and that are easy to express, but that are fiendishly difficult to prove. Here are some of our favourites.