Is 9 a rational number?

$9$ is a rational number.
Rational numbers are those numbers which can be expressed as $\frac{p}{q}$, where $p$ and $q$ are integers and $q \ne 0$..
As all natural or whole numbers, including $9$, can also be written as fractions $\frac{p}{1}$ they are all rational numbers.
Hence, $9$ is a rational number.