Is there some magical value for having 12 apostles as opposed to 13 or 100?
What is clear through scripture is there was a much larger group of "hangers on" surrounding Jesus during his ministry. What separated that group from "the twelve" and the selection of Matthias from amongst them after Judas died?
Yes of course we all know about the 12 tribes of Israel but we also know that the 12 did not in fact represent all the tribes.