Remember... I am not talking about symbols. I am talking about what the symbols represent.
Numbers are symbols.

They represent a quality of a group of objects.

The only question with any sort of meaning related to yours is 'which was the first number which could be correctly applied in the history of the universe to a group of objects'. There is no real answer to this, you could assign all sorts of numbers to different qualities of the beginning of the universe.

The groups of objects which numbers describe are real. The numbers themselves are not real (real in a physical sense, not technical mathematical sense).