If one bitcoin could buy all the wealth in the world, it would make the other 20999999 worthless. It's not logically possible.
Technically it is possible. If the remaining coins are lost (eg sent to 1BitcoinEaterAddressDontSendf59kuE by mistake), and all other world currencies become obsolete, then that last remaining bitcoin would represent all the wealth in the world.
Technically maybe, but not logically. It might be technically possible to send 20999999 bitcoin to the bitcoin eater, but it's not logical is it?