Apparently a $3,000 GIMPS research discovery award. What's the practical utility of knowledge of a prime, especially considering that upon announcement it's immediately disseminated?
It's a very large prime number which has a very convenient representation, which makes it useful. You could use it in a Mersenne Twister RNG, for instance.
The point of searching for these primes is to motivate research in finding primes so there isn't much practical utility.