And I'm sure those employees who made the right choice and walked out of your interviews don't have space for you.
You can have hundreds on your team and still be an asshole who doesn't know how to treat a potential employee with respect and ask them serious questions. That person who walked out had the right answer... that you were not asking a serious question. Perhaps they handled it poorly, but they dodged a bullet if that is how you manage a team, with clown questions thrown out at random.
If you don't treat your potential employees seriously, why should they treat you seriously? Do you run a circus?
If you asked me that question, I would look at you and politely ask for a clarification. "I'm sorry, maybe I misunderstand. Do you really want to know the answer to that question?"
If you said yes, I'd whip out my phone, google it (approx 160,00 - there, I just did it) and give you the answer. The correct answer.
"I don't know" is not the correct answer; that is akin to answering a jeopardy question with "who are three people who have not been in my living room." It's a glib response that makes the too-clever-by-half interviewer feel smug that they asked a clever question, and that the interviewee paused for a moment to admit their ignorance. But ... and this is important ... it's not the correct answer. If you are asking a serious question.
If you said "no, not really" then I would politely wonder why you would ask me a question you did not want an honest answer to, and then immediately start to question the seriousness of the interview, and whether or not that job is one I would truly want.
If you said, "I really don't care about the correct answer; I'm really trying to determine your approach to problem solving," I would politely point out that "How many gas stations there are really isn't a problem to solve, in my opinion, it's a trivia question, for which a search will provide the correct answer, which is, let's see... 160,000."
Being proud of yourself for being unserious and dishonest to your potential employees is not a sign of professionalism. There's nothing wrong with curveball questions... but you shouldn't be surprised if they give you a curveball answer, should you?