Question

Why isn't $57$ a prime number?

Answer 1

$57$ is not a prime number

A prime number is an integer that has exactly two factors. If $p$ is a prime, then the only factors are $1$ and $p$.

Any number that does not obey this rule is referred to as a composite number.

$57=3\times 19$

So, the number $57$ is divisible by $1,3,19,57$.

Hence, 57 is not a prime number because it has more than two factors, namely $1$, $3$, $19$, and $57$.