1

The number one (or 1 in decimal form) is the second non negative integer, the first positive integer, and the number following 0 and preceding 2 on the number line. It is extremely simple for the vast majority of humans to visualize one of something (or one object).

It is the first number to appear in many integer sequences, such as the square numbers, triangular numbers, and the cube numbers. It's also the first two Fibonacci numbers!

In basic arithmetic, one is known as the multiplicative identity - that is, any number n multiplied by 1 will always equal n.