Numéro 9

DR. JAMES GRIME: So we're going to do a little mathematical trick that I'm hoping that people will like and they'll try out on their friends and family. So let's do it....

BRADY HARAN: So we're going to talk about the number 8,128. And it's a famous type of number called perfect number. Now, this was the largest perfect number known in antiquity, or for...