81565600891 has 8 divisors (see below), whose sum is σ = 86413044240. Its totient is φ = 76723653888.

The previous prime is 81565600847. The next prime is 81565601081. The reversal of 81565600891 is 19800656518.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 81565600891 - 2²⁹ = 81028729979 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81565600801) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1343506 + ... + 1402903.

It is an arithmetic number, because the mean of its divisors is an integer number (10801630530).

Almost surely, 2^81565600891 is an apocalyptic number.

81565600891 is a deficient number, since it is larger than the sum of its proper divisors (4847443349).

81565600891 is a wasteful number, since it uses less digits than its factorization.

81565600891 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2748173.

The product of its (nonzero) digits is 518400, while the sum is 49.

The spelling of 81565600891 in words is "eighty-one billion, five hundred sixty-five million, six hundred thousand, eight hundred ninety-one".