[nitwit005]

Very few of us have had to do difficult math in a high pressure social situation. Having someone sitting there and pushing for instant answers is just going to sink most candidates for no real reason.

I've found you often need to directly ask the interviewer not to do what they're doing when they try this sort of thing. Sometimes they're just bored and want to talk because there has been a moment of silence, or because they're enamored with their interview question.

[arandomusername]

Difficult math? You just have to multiply 2s until you reach >56mil, and you can just round up (i.e 16k -> 32k -> 64k).

[nitwit005]

Difficult enough to need some time to think, yes.

If it was trivial, there'd be no point in asking.

[arandomusername]

Few minutes maybe.

It's a beginning question to get you warmed up.