The answer to the universe
A mathematician was explaining bases to me. We use base 10, presumably because we have 8 fingers and 2 thumbs, so the number 10 means 1 lot of 10 and 0 more units, whereas 11=1 lot of 10 plus 1 unit and 34=3 lots of 10 plus 4 units. You get my drift.
Anyway, the mathematician said that if you change the base from 10 to 13, the answer to the universe, 42, is 6 x 9 because 4 x 13 is 52 plus 2 is 54.
I was sceptical and was comforted to read on Google that Douglas Adams said, "The answer to this is very simple. It was a joke. It had to be a number, an ordinary, smallish number, and I chose that one...A completely ordinary number, a number not just divisible by two but also six and seven. In fact it's the sort of number that you could, without any fear, introduce to your parents... I may be a sorry case, but I don't write jokes in base 13."
So there you have it.