Earlier quoted context omitted.
If the candidate says they don't know a topic, that is a valid response. It's not worthwhile to ask detailed questions about the topic. That's a sign of an inexperienced and/or unprepared interviewer.
Asking someone "how many prime numbers are there?" seems pretty valid to me. It's an easy question. The two valid answers are: "a lot" or "infinite" (with "more than 10" also being a fine answer IMO). I'm not sure the interviewer was expecting the actually correct answer here (infinite) - lots of programmers don't know that there are infinite prime numbers - I think he was trying to set up for an explanation of an al…
I said I knew nothing when he asked about number theory. I never tried to cover up anything in my gaps. The interviewer proceeded to ask questions about it.
I don't have a CS degree, I have never claimed I did or that I enjoy or even want algorithms heavy jobs. This was an internal tool to manage datacenter component ordering.
I would never ask a bunch of questions about something borderline esoteric to someone that has already said they don't know anything about the field. I have had plenty of interviews where I am doing the hiring and when I realize the candidates are in over their heads I politely ask some fielding questions (like, do you know number theory is great, and fair) and then just conclude the interview kindly or toss them a different set of questions depending on how the interview has been going.