It is safe to assume that any well-prepared candidate has at least visited your website to find out more about your organisation (if they haven’t that is a bit of a red flag); but such a question helps give you some insight into the preparation efforts of the candidate…
Follow this with a supplementary question: What else would you like to know about our company?
How this question is answered can tell you a lot; if they have questions then this is a good sign of someone who is inquisitive and engaged, someone with an active mind. It can also give you insight into what within the company or what it is about the role that they are particularly interested in.
If they have no questions this is not necessarily a bad thing; watch how they answer it: if they respond confidently acknowledging they have no questions this is I think is good – I particularly like it when the candidate refers to information already shared in the interview, a sort of summary statement. Also, if they have shared pretty comprehensive background research when you initially asked the opening question, perhaps it is real that there is nothing left to ask about.