Still, whether or not the question was valid/appropriate/useful doesn't really matter. On the job, sometimes you will be asked things you don't know, or things

Still, whether or not the question was valid/appropriate/useful doesn't really matter. On the job, sometimes you will be asked things you don't know, or things you shouldn't even be responsible for knowing. The way this person responded to receiving a question like that indicates that they might be a difficult person to work with. The interviewer sounds probably bad. After the person made it clear they didn't know about number theory, they should have moved to a different topic. But still, answering "Optimus prime" just suggests immaturity or even combativeness in the face of a difficult situation, which isn't someone you want to hire. There are a thousand better answers. Even snarky answers are fine as long as the person is meaningfully engaging. "I don't know. Probably a lot" "Maybe infinite. I'm not sure." "It's an interesting question. Am I allowed to look it up?" (As someone else said) "Definitely more than 10. Outside of that I'm not sure." "I don't know. But here is how I would write a script to figure it out" It comes back to the "move mt. fuji" style questions mentioned in the article. The point of an interview is not to determine whether you would be able to move mt. fuji anymore than whether you are able to answer the number of primes. It's about how you communicate and approach a problem. "Optimus prime" is such a non-starter that it doesn't even allow for a discussion. I'm speaking as someone who passed a google interview and worked there for several years, so there may be some reason to believe my feelings around interview approaches are based in fact.