Consider the following sentences:
Enough are present to form a quorum.
Not enough are present to form a quorum.
M-W and Wiktionary both label
enough as a pronoun in this usage, but they also label
not as an adverb. How can
not be an adverb, if it's modifying a pronoun?
Perhaps more importantly, is this question about anything semantically meaningful under the surface, or is this just an arbitrary decision?