Is enough a noun

No, the Word 'enough' is not a noun. The Word 'enough' is an adjective, an adverb, an indefinitepronoun, and an interjection.

Examples:
There's no such thing as enough chips in the cookies. (adjective)
If you drive far enough north, you come to the river. (adverb)
You may have some, we have enough for everyone. (indefinite pronoun)
Enough! It's starting to spill over the top. (interjection)