The Riemann Hypothesis is one of the most famous problems in that set. It’s about prime numbers. That’s any whole number that can only be divided by 1 and itself – like 2, 3, 5, 7 and 11.

It doesn't matter how gifted you are at math, this children's homework question is bound to leave you baffled, just like the millions of puzzled internet users who can't comprehend it. In a now viral ...