Can I somewhere see the number of registered users on our site [ without multiplying the number of pages by 36, the number of users per page] ?
A possible way to get an idea about this number is to look at the right (i.e. total reputation tab) of this page. As of today, it seems that there are $65\,508$ registered users.
On the other hand, I am sure that a lot of people create new account for every new question they have, and therefore the number of actual users is (much?) less than the number of registered accounts.