I was pondering about what are the numbers. It seems like a number is data type. I mean, like Maybe in Haskell. Because, for instance, one on its own means nothing for me. However, one apple tells me about how many apples does one talking about. Thus, numbers are quite abstract. If somebody asks you "how is it going" you can't answer "10". 10 what? But you could say 10 out of 10. But this is another abstraction. So, what I want to say is that a number is an abstraction. It can only be used to quantify other things. Thus, very often people say that "Number" is a type or set or category, etc. But then if a concrete number is an abstraction what is Number?
I hope you've got my idea and question and sorry if I used some terms incorrectly. I'm trying to study CS on my own and do make lots of mistakes.