81518566679 has 4 divisors (see below), whose sum is σ = 88929345480. Its totient is φ = 74107787880.

The previous prime is 81518566609. The next prime is 81518566681. The reversal of 81518566679 is 97666581518.

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 81518566679 - 2¹² = 81518562583 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81518566609) 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, 3705389384 + ... + 3705389405.

It is an arithmetic number, because the mean of its divisors is an integer number (22232336370).

Almost surely, 2^81518566679 is an apocalyptic number.

81518566679 is a deficient number, since it is larger than the sum of its proper divisors (7410778801).

81518566679 is a wasteful number, since it uses less digits than its factorization.

81518566679 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7410778800.

The product of its digits is 21772800, while the sum is 62.

The spelling of 81518566679 in words is "eighty-one billion, five hundred eighteen million, five hundred sixty-six thousand, six hundred seventy-nine".