1729 is the smallest number you can write as the sum of two cubes, in two different ways.
One is the most popular number, as it appears more often than any other number.
Six is often treated as 2x3, but has many characteristics of its own.
Are 4 colours enough to paint any map, so neighbouring countries have different colours?
Are 7 shuffles sufficient to achieve a good degree of randomness in a deck of 52 cards?
Doubling is a form of exponential growth, which appears in population growth and inflation
Melvyn Bragg examines the number between 1 and -1, once denounced as the devil's work.
Strangely, 'nothing' had to be invented, and then it took thousands of years to catch on.