Unnatural in the sense of "Young man, in mathematics you don't understand things. You just get used to them". Or in the general sense of science, you work hard to get intuition that is against what you get from your daily experience, such as feather and iron ball fall at the speed in vacuum, electrons interact with electronic field, there exist functions that are continuous everywhere but not derivative anywhere, light of spped is constant in all reference frames, or simply high school algebra is really simple (and has been watered down for years) and most of kids should have no excuse not to excel at it.