Mersenne Primes are named after Marin Mersenne, a 16th century theologian, referred to as the 'father of acoustics', but known for his discovery of a special set of prime numbers. Mersenne Primes are in the form of 2^n +1. In the case of the 46th Mersenne Prime, n = 43,112,609.
Every once in awhile a new Mersenne Prime is found. When in college, a fellow student printed, what was probably the 30th Mersenne Prime, on a dot-matrix printer, and hung it up on a wall in the math wing of the university. It took pages of paper to print the entire number.
In contrast, the 46th Mersenne Prime, found this month by a group at UCLA, is over 13-million digits long and would take about 10 weeks to write down, a digit at a time. It took 75 PCs running Windows XP to generate the prime number. It is the 8th such prime discovered at UCLA.