Is the Riemann Hypothesis hard to understand?

I read a book about the Riemann Hypothesis, more of a book telling the story, but it explained in elementary form some of the math involved. But atleast at the very minimum, what areas of mathematics do you need to understand before you can truly understand what Riemann ment in his famous hypothesis? I mean as it was when he first postulated it, discluding all the mathematical subjects neccesary to understand the research done on the hypothesis in the modern time.