I think his number is the same number of the whole house.
Changing the subject, I know this is a cartoon and that things on here are exagerated sometimes, I don't know if this was discussed before, but a question -well, many questions- came to my mind a short time ago.
How can all Wilt's organs fit on his thin body? Were are his lungs, stomach, etc.? I mean, does the food go into his feet?.. I'm sorry!, I'm sorry! That was awful! I'm terrible! I don't think that actually happens! *runs towards the wall and hits her head with it, then she runs into the kitchen and spills lemon juice on her eyes. She returns to the computer* I had to punish myself... In what was I? Oh, yes... SORRY! I'm sorry! I didn't mean to!... Well, let's continue.
And what about his ribs? Wouldn't they have to be really thin so they fit? And something REALLY important, how can his heart fit in there? At least on all of us, human beings, our heart has a similar size to our fists, and have you seen the size of Wilt's fists? I'm sure you have. But maybe, like in other living things, that does not apply to him.
Maybe Mac, Goo, Cheese and many other imaginary friends and children are more or less as "fat" as him, but they are much shorter.
So... in conclusion, how can everything fit there, on his body? Only the cartoon's "magic"? Do you think there might be another explanation?