The largest known prime numbers are Mersenne primes, the largest of these known as of September 2013 bing , which has a whopping decimal digits.

As of Sep. 2013, the largest known probable primes are the Wagstaff primes and , both found by R. Propper in Sep. 2013 and which have and decimal digits, respectively. Other large known probable primes are the "dual Sierpinski numbers" (Moore 2009) given by and , which have and decimal digits, respectively.

A prime with at least 1000 decimal digits is (or used to be) known as a titanic prime.