I am really obsessive about numbers, and a lot of the time I won't do something if it has a certain number associated with it.
Anything that has a 5,0, has a pattern (like 33) or is even (though 6 is my least favourite even number) is fine. But odd numbers (except 5 and especially 13) drive me nuts. In math I'll be fine, but I can't have 3 pages on a report (I'll make it 2,4, or even 3.5) and I either take 11, 15, or 22 seconds while drinking at the water fountain. I don't have any compusions, so it's not OCD (I only have a few other symptoms that would work for the obsessive part of OCD, so I don't think I would get a diagnosis even if their was an Obsessive Disorder)
So could this be an Autism thing or something else?