http://en.wikipedia.org/wiki/Largest_known_prime_number
http://www.youtube.com/watch?v=M4vqr3_ROIk&edufilter=r4lcrtNm3zVmeGFQEW6B2A
http://www.youtube.com/watch?v=YCuXiujC3KE&edufilter=r4lcrtNm3zVmeGFQEW6B2A