How hard is this class?

I hear it's one of the toughest undergraduate classes in any major. I won't be taking it until next fall, but I want some opinions about the class. I want to see what is generally a prerequisite for the class(I'm taking Number Theory and Abstract Algebra now along with Applied Probability and Statistics in the summer) and what background knowledge is needed.

I'm honestly scared to death about this class. If things go as planned, after summer, I'll only have 3 400-level math classes to finish before my degree.