81516257913 has 4 divisors (see below), whose sum is σ = 108688343888. Its totient is φ = 54344171940.

The previous prime is 81516257909. The next prime is 81516257929. The reversal of 81516257913 is 31975261518.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 81516257913 - 2² = 81516257909 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (81516257903) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 13586042983 + ... + 13586042988.

It is an arithmetic number, because the mean of its divisors is an integer number (27172085972).

Almost surely, 2^81516257913 is an apocalyptic number.

It is an amenable number.

81516257913 is a deficient number, since it is larger than the sum of its proper divisors (27172085975).

81516257913 is a wasteful number, since it uses less digits than its factorization.

81516257913 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 27172085974.

The product of its digits is 453600, while the sum is 48.

The spelling of 81516257913 in words is "eighty-one billion, five hundred sixteen million, two hundred fifty-seven thousand, nine hundred thirteen".