81928665 has 168 divisors, whose sum is σ = 192018240. Its totient is φ = 32752512.

The previous prime is 81928663. The next prime is 81928681. The reversal of 81928665 is 56682918.

It is not a de Polignac number, because 81928665 - 2¹ = 81928663 is a prime.

It is a super-2 number, since 2×81928665² = 13424612297364450, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a self number, because there is not a number n which added to its sum of digits gives 81928665.

It is not an unprimeable number, because it can be changed into a prime (81928663) by changing a digit.

It is a polite number, since it can be written in 167 ways as a sum of consecutive naturals, for example, 4312026 + ... + 4312044.

Almost surely, 2^81928665 is an apocalyptic number.

It is an amenable number.

81928665 is an abundant number, since it is smaller than the sum of its proper divisors (110089575).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

81928665 is a wasteful number, since it uses less digits than its factorization.

81928665 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 75 (or 47 counting only the distinct ones).

The product of its digits is 207360, while the sum is 45.

The square root of 81928665 is about 9051.4454646758. The cubic root of 81928665 is about 434.3221308944.

The spelling of 81928665 in words is "eighty-one million, nine hundred twenty-eight thousand, six hundred sixty-five".