How long does it usually take for everyone to reply to the internship interview?

As for the time when the results of the internship interview come out, it depends on the specific situation. Some big companies have to wait until all the people in the country have finished interviewing before selecting outstanding talents, so the result may be a little late, about a week or two, and some companies that don't need to recruit too many people will reply faster, about two or three days. But if you haven't received the interview results after two weeks, I suggest you send an email or call the internal recruiter.