Some may call a number a mathematical entity, others may just hold up their fingers. Are we to take the apparent existence of what we call our "ten" fingers to be proof of the existence of numbers? Are numbers perhaps only something which exist as abstract entities in the human mind? What do you think?
Numbers are there, but the arab-numeric numbers we use are just the language our mind uses to keep track of them. If you did not have the ability to realise that 2 objects are in front of you does not mean that they are not. unless you're one of those people who think that reality is a complete illusion created by your brain. >.>
I can't go in depth and start reading, unfortunately, as I've got an essay due in eight hours and I've yet to start, but I direct your attention to this page. I would specifically point to sections 2.2 and 2.3, but I really haven't read very much on that page. I look forward to reading what you all make of that (if you choose).
A number is similar to a letter in the alphabet in the language of mathematics. That simple. Math is a language and numbers are what is used to speak the language.