Yes, the number "18000" is a natural number as it exists in the collection of the natural numbers in the number line.
\[\begin{align}
& N=\left\{ \ 1,\ 2,\ 3,\ \ldots +\infty \right\},\text{ where} \\
& \infty \text{ denotes infinity and + indicates positive value or direction} \\
\end{align}\]
Regular exam updates, QnA, Predictors, College Applications & E-books now on your Mobile