Alex Bellos, one of our favourite maths authors, recently conducted a survey to find the world's favourite number. After polling more than 30,000 people from around the world, he found that the winner was ... 7!

We rather like 7 ourselves and decided that this is because 7 is the first prime number that really "feels" like a prime number, and because it's the most common result you get from throwing a couple of dice. Alex has come up with a different reason — see the video below. To find out more about the poll, see favouritenumber.net or read Alex's new book Alex through the looking glass (reviewed in Plus).