Ouch. I see your problem. I didn't see the word numb"er" in the dictionary as a comparative form. Maybe you could put it in quotes. I don't think numer is a word. I'm stumped. Sorry.
You could do any of these:
numb'r
"numb"er
"number"
or just plain ol' number. I think it makes sense in context. No one will think of the word for numeral over the comparative of numb because it's obvious he means numb. I wouldn't worry about it.