Largest known prime number discovered

Well, who'dathoughtit? They are still discovering new prime numbers. More to the point, perhaps, some people out there are still LOOKING for prime numbers.
Using a program called Prime95 on a really fast computer, volunteer John Pace from Tennessee, has proved that 2^77,232,917 - 1 is a prime number (that's 2 multiplied by itself 77,232,917 times, and then subtract 1 from the result). It is one of a special class of prime numbers called Mersenne primes, i.e. prime numbers of the form 2ⁿ - 1, named after the 17th century French monk Marin Mersenne, who was the first to discover this method for identifying prime numbers. It is only the 50th Mersenne prime ever to be discovered.
The actual number Mr. Pace discovered has 23,249,425 digits, so forgive me for not showing it here (it is apparently long enough to fill a whole shelf-full of books, totalling 9,000 pages). Indeed, it is nearly a million digits longer than the previously discovered Mersenne prime, and it took six full days of computer processing to come up with the proof. Mr. Pace is one of thousands of volunteers for the Great Internet Mersenne Prime Search (GIMPS), the shady organization established in 1996, which has been responsible for finding the last 16 Mersenne primes.
It kind of warms the heart to know that there are people out there frantically searching for such phenomena, which have no known practical use. Good job, John!