81928865 has 16 divisors (see below), whose sum is σ = 106641360. Its totient is φ = 60180480.

The previous prime is 81928859. The next prime is 81928867. The reversal of 81928865 is 56882918.

It can be written as a sum of positive squares in 8 ways, for example, as 1216609 + 80712256 = 1103^2 + 8984^2 .

It is not a de Polignac number, because 81928865 - 2⁶ = 81928801 is a prime.

It is not an unprimeable number, because it can be changed into a prime (81928867) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 8270 + ... + 15239.

It is an arithmetic number, because the mean of its divisors is an integer number (6665085).

Almost surely, 2^81928865 is an apocalyptic number.

81928865 is a gapful number since it is divisible by the number (85) formed by its first and last digit.

It is an amenable number.

81928865 is a deficient number, since it is larger than the sum of its proper divisors (24712495).

81928865 is a wasteful number, since it uses less digits than its factorization.

81928865 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 23572.

The product of its digits is 276480, while the sum is 47.

The square root of 81928865 is about 9051.4565126282. The cubic root of 81928865 is about 434.3224843090.

The spelling of 81928865 in words is "eighty-one million, nine hundred twenty-eight thousand, eight hundred sixty-five".