Set of Natural Numbers is Ordinal

Theorem
The set of natural numbers $\N$ is an ordinal.

Proof
From Natural Number is Ordinal, every element of $\N$ is an ordinal.

From Union of Set of Ordinals is Ordinal, $\bigcup \N$ is therefore itself an ordinal.

From Set of Natural Numbers Equals its Union:
 * $\bigcup \N = \N$

Hence the result.