Normally I would avoid maths problems where scientists start off by saying: "The numbers involved are so enormous that if their digits were written out by hand they would stretch to the moon and back."

Thankfully there are people who are challenged by such numbers and this week a group of such researchers said they, through a technique for multiplying large numbers, have figured out congruent numbers up to a trillion. Apparently no one had taken them beyond a billion for some reason.

In case you were wondering, a the first few congruent numbers are 5, 6, 7, 13, 14, 15, 20, and 21. The problem, which was first posed more than a thousand years ago, concerns the areas of right-angled triangles. The difficult part is to determine which whole numbers can be the area of a right-angled triangle whose sides are whole numbers or fractions. The area of such a triangle is called a "congruent number."

rest here