Numbers and the human brain

Something that I realized while working on exercise 9, is that it is quite mysterious how the human brain represents and deals with numbers, or more generally, quantities. While concepts and entities are fairly discrete things, numbers are more slippery. While they are discrete, to a certain extent, there are an infinite number of them. ie. You can't create an entity in the brain to represent each one. How do you create a kind of generic entity in the brain to represent any given number?

I have cheated in a sense, since I have implemented numbers using the computer's internal representation. I think this is the most sensible thing to do: Why lament on why the computer makes some aspects of intelligence easier?!

On a related note, I am pondering how to create a scheme to transform numbers like "five hundred and twenty three" into the brain's internal representation.