31 and Mersenne Primes

Alex Bellos discusses how the Incans used knots in string (Quipu) to record numbers.Check out Brilliant (get 20% off their premium service): https://brillian...

31 is one of the special Mersenne Prime numbers. They are related to perfect numbers.

See our perfect number video at http://www.youtube.com/watch?v=ZfKTD5lvToE

This video features Dr James Grime.

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