6174

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...

6174 is also known as Kaprekar's Constant.

This video features University of Nottingham physics professor Roger Bowley, who is also featured on our Sixty Symbols channel at http://www.youtube.com/sixtysymbols