You didn't need a math professor to tell you that, no matter what the song
says, one is not "the loneliest number." (But if you actually do
need a math professor to tell you, Dr. Mason Porter of UCLA is there for you
.) The lyric needs text doctoring, since one divided by two is in fact a half (.5):
Original: One is a number divided by two.
Revision: One's the remainder when you once halve two.
If we do say so ourselves, our revision offers not only homophony (one's/once) but also wordplay (halve/have). (Don't knock us, for if we received even half the literary criticism we deserve, we wouldn't have to analyze our own work. Hint: this is your invitation to be part of the solution.)
Our headline from Greensboro's 1975 yearbook.