Well, yeah, numbers do. (They are not all primes anyway, e.g., 99.)
There are, in fact, a finite number of achievements, and as long as they're designing badges for them, this will continue to be true.
So it is entirely possible for there to be a page where I can find out which ones I haven't completed yet. Right now, my own page of achievements is listing them in order of completion, but the encyclopedia lists them in alphabetical order. So it's hard to tell what's missing.