Well, it's "generally suspected not to be NP-complete", Wikipedia has a citation. I guess if you proved that it is or is not NP-complete, that would be a significant result...

Fair enough.  I probably should have made that clear in the text.  What I meant was that if you could solve an NP-complete problem fast enough that you could also solve integer factorization problems.  Even though it's probably not NP-complete, it's definitely in NP.