Of the seven Millenium Math Problems, each of which is worth $1 million to the person who can solve it, the Riemann hypothesis is perhaps the most difficult to crack. Reckon you've got what it takes?
In this video, my favorite mathematician, Edward Frenkel, explains the basics of the theorem. If you can puzzle through it, you could make yourself a packet—but it might just be the hardest $1 million you ever make. [YouTube]