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# Natural numbers and integers

The positive whole numbers are the numbers that we use for counting. They are called the natural numbers.

$1$ and $10$ are natural numbers. $3.2$, $1/4$ and $-1$ are not.

The positive and negative whole numbers are collectively called integers.

$-1$, $-10$ and $5$ are integers. $-1/3$ and $2.4$ are not

The set of the natural numbers is written as $\mathbb{N}$. The set of the integers is written as $\mathbb{Z}$.

There are infinitely many integers.

This Babylonian clay tablet shows arithmetic using natural numbers. Babylonians also used fractions and square roots, but no negative numbers or zero.