 , 51 Mersenne primes are known, and therefore 51 even perfect numbers (the largest of which is 282589932 × (282589933 − 1) with 49,724,095 digits).It is not known whether there are infinitely many perfect numbers, nor whether there are infinitely many Mersenne primes.As well as having the form 2"p"−1(2"p" − 1), each even perfect number is the triangular number (and hence equal to the sum of the integers from 1 to ) and the hexagonal number.