of which the number

Which are correct:

[color=red]1-Assume there is a box full of books, and you have been told the number of the books.
[color=indigo]2-Assume there is a box full of books, the number of which you have been told.
[color=blue]3-Assume there is a box full of books, of which the number you have been told.
[color=darkblue]4-Assume there is a box full of books, whose the number you have been told.

Gratefully,
Navi.

1 and 2 are correct.

3 would need to be:
Assume there is a box full of books, of which you have been told the number.

‘whose’ doesn’t work with an object
Assume there is a girl, whose address you have been given
is an equivalent structure. (note there is no article after ‘whose’)