Same story here. I was actually a math major and took the general GRE (which I believe is what we are discussing) in my senior year. I only studied the night before, just to see if their prep guide included any funky vocab or other memorization questions. I looked at some vocab, spent 10 minutes reviewing geometry and trig identities, and called it a night. Turns out I didn't even need any of it.
(I did get one question wrong, though, and looking back I definitely know which one. It was an easy one in the middle of the exam questions and I think I just messed up a concept like "less than" instead of "less than or equal to".)
All my math/C.S. friends thought it was really easy and I think the worst score I heard from them was 720 / 800.
Interestingly, though, back when I took it the average score for the math section was notably higher than for the other sections. Just by missing 1 question I think I was bumped down to about the ~90% percentile.