To me a Credit Card Number isn’t actually a number at all…if you see what I mean.
It’s actually, the way I see it, a text string (or 4 text strings if you like).
You aren’t going to do any manipulation of the number so there really isn’t any need to treat it as one.
Anyway, here’s an article on HTML5 inputs…’number’ is about half way down.
The article actually references an old video by Chris Coyier.