Is it possible to write a command that will create a team with a team name that it doesn't know yet? For example: if I want to create a new team for each player that joins, and I have a scoreboard counter (represented as X) starting at 0, would I be able to give their newly-generated team the name "X"?

So it would go:
> there are 0 players. X=0
> new player joins
> X=1
> new team is created. its name is "1"
> the new player join team "1"
> new player joins
> X=2
> new team is created. its name is "2"
> etc.

Furthermore, is this possible with tags? So the exact same thing but I would store the value of X in an entity's tag data.

Any help is appreciated.