As Six implied, they're the last algebralian in the equation playground, the question stands from where everyone went. We know that 1 is in their pocket dimension while 2, 4, and X are hosting TPOT. The other numbers, have to be somewhere. It is a possibility that they all have portals like 1 & 4 and just left through there, but there's only 2 door in the playground so...

I just wanted to know your opinions on this.