The mark won’t be a literal number. The mark on the head represents what you believe, and the mark in your hand represents your actions. In other words if you are not saved, you are already marked. Just as God will seal the names of those saved and place his mark upon them. Remember what the Bible says? All those not saved and found in the book of life will worship the beast and receive his mark. If you ain’t with God you’re with the other guy.
Doesn’t God already know how all this will end? If so, then He already knows who is with Him or not, doesn’t He?
You are over allegorizing what is a very specific prophecy and a very specific calculation, the Bible is very specific as to what happens to those who take the mark...it is not specific as to what happens to those who don’t take the mark but yet still survive to HIS GLORIOUS APPEARING. The “book of life” judgment doesn’t occur for a millenia or so after the Beast is destroyed and Satan who has been chained, is “loosed for a season”. Another words, after Armegeddon, it aint over yet!