I don't think it's fair to tell them "Divide by x" or whatever because that's not what the boss actually does. He uses an ability called "Divide by x," which is the cast bar, while explicitly saying (in chat as well as an onscreen pop-up) "Calibrate vitals to multiples of x." He literally tells you what to do if you read -- it's not like you have to "figure it out" beyond finding out that standing in the circles changes your hp.

Also, how does a group of math majors think that 1 is a prime number? I have a hard time believing that any competent math major wouldn't understand the fundamental theorem of arithmetic well enough to know that 1 isn't defined to be prime.