51318585991 has 4 divisors (see below), whose sum is σ = 51465631000. Its totient is φ = 51171540984.

The previous prime is 51318585959. The next prime is 51318586021. The reversal of 51318585991 is 19958581315.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 51318585991 - 2⁵ = 51318585959 is a prime.

It is a super-2 number, since 2×51318585991² (a number of 22 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (51318585691) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 73521981 + ... + 73522678.

It is an arithmetic number, because the mean of its divisors is an integer number (12866407750).

Almost surely, 2^51318585991 is an apocalyptic number.

51318585991 is a deficient number, since it is larger than the sum of its proper divisors (147045009).

51318585991 is a wasteful number, since it uses less digits than its factorization.

51318585991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 147045008.

The product of its digits is 1944000, while the sum is 55.

The spelling of 51318585991 in words is "fifty-one billion, three hundred eighteen million, five hundred eighty-five thousand, nine hundred ninety-one".