Full Idea
Numbers are not 'abstract' (in the old sense, of universals abstracted from particulars), since each of the integers is a unique individual, a particular, not a universal.
Gist of Idea
Numbers are not abstracted from particulars, because each number is a particular
Source
James Robert Brown (Philosophy of Mathematics [1999], Ch. 2)
Book Reference
Brown,James Robert: 'Philosophy of Mathematics' [Routledge 2002], p.12
A Reaction
An interesting observation which I have not seen directly stated before. Compare Idea 645. I suspect that numbers should be thought of as higher-order abstractions, which don't behave like normal universals (i.e. they're not distributed).
Related Ideas
Idea 645 If two is part of three then numbers aren't Forms, because they would all be intermingled [Aristotle]
Idea 8311 If 2 is a particular, then adding particulars to themselves does nothing, and 2+2=2 [Lowe]