The crisp new dollar bill that I have just taken from my wallet bears the serial number 24598176. It’s easy to tell that the number is exactly divisible by 2 but not by 5. Is it divisible by 3? by 4?

Earlier today I set you these three problems about the number 11. Here they are again with solutions. 1. Funny formation You are the coach of a football team, whose players have shirt numbers 1 to 11.

It’s two decimal digits long, it’s prime, it’s a palindrome and it’s the number of players in a football team. Let’s hear it for “legs” eleven! Today’s puzzles reveal interesting properties about the ...