73 to the 12th power is how much? Rudiger Gamm knows. Also 54 to the 17th power. Watch.

YouTube link.

This is Rudiger Gamm.  What's interesting is that even though he is a mental calculator, for this television show he appears to be not calculating the numbers, but rather reciting them from memory.

From his head motion I would also wonder if he has an eidetic memory and is seeing the number in his mind and reading it out loud.