Residue class rings of Z/Field/Integer/Prime number/Fact

Let ${}n\geq 1$ be a natural number, and let ${}\mathbb {Z} /(n)$ be the corresponding residue class ring.

Then the following statements are equivalent.

1. ${}\mathbb {Z} /(n)$ is a field.
2. ${}\mathbb {Z} /(n)$ is a domain.
3. ${}n$ is a prime number.

Write a proof