I'm currently doing 13 million digit calculations

... or at least my computer is. I signed up for the GIMPS project to look for new Mersenne Prime Numers. There are only 40 of these numbers that are known. The most recently discovered one is 13 million digits long. The GIMPS project runs calculations on computers that are registered for this project. If you discover a new Mersenne Prime Numbers you get the credit and the glory that comes with it.