The concept of number is very sophisticated; humans got on fine for a long time without using 'digits', as such.

Once we get as far as writing numbers down we get into Maths. Maths is an intellectual engine which manipulates abstract things and (mostly) the results can be injected back into the real world to give a valid answer.

Without resorting to this higher intellectual level that Maths provides for us, I think we would not be able to 'count' up to more than four or five, in an innate way. For any more than this, it becomes a different exercise and we can only directly appreciate comparative numbers ('more' or 'fewer') in a fuzzy, analogue, sort of way.

Of course, where the objects are grouped in some way, the problem becomes much easier. Our brains do their very best to make sense of things and Maths (arithmetic) is a set of rules to allow us to make a major step in complexity.

We take it for granted that we can count and appreciate numbers but the fact that children have to be taught to count implies that it is not innate but cultural.