while the term prime number commonly refers to prime positive integers other types of primes are also defined such as the gaussian primes the number 1 is a special case which is considered neither prime nor composite wells 1986 p 31arge primes caldwell include the large mersenne primes ferrier s prime and the digit counterexample showing that 5359 is not a sierpiÅski number of the second kind helm and norris the largest known prime as of january 2013 is the mersenne prime which has a whopping decimal digits