The newest prime number, found recently by a student at Michigan State University, is by far the largest yet. The number ([2 to the power 20,996,011] minus 1) has more than 6m digits (2m more than the previous largest number) and belongs to a special class of rare numbers known as the Mersenne primes.

It is only the 40th such prime to be found and is named after Marin Mersenne, a

17th-century French monk who first studied the numbers more

than 300 years ago. Prime numbers are widely used to produce encryption codes on the Internet. — The    Guardian