81691875 has 80 divisors (see below), whose sum is σ = 155950080. Its totient is φ = 42228000.

The previous prime is 81691853. The next prime is 81691889. The reversal of 81691875 is 57819618.

It is not a de Polignac number, because 81691875 - 2⁷ = 81691747 is a prime.

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 81691875.

It is an unprimeable number.

It is a polite number, since it can be written in 79 ways as a sum of consecutive naturals, for example, 793074 + ... + 793176.

It is an arithmetic number, because the mean of its divisors is an integer number (1949376).

Almost surely, 2^81691875 is an apocalyptic number.

81691875 is a deficient number, since it is larger than the sum of its proper divisors (74258205).

81691875 is a wasteful number, since it uses less digits than its factorization.

81691875 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 179 (or 158 counting only the distinct ones).

The product of its digits is 120960, while the sum is 45.

The square root of 81691875 is about 9038.3557686119. The cubic root of 81691875 is about 433.9033015964.

The spelling of 81691875 in words is "eighty-one million, six hundred ninety-one thousand, eight hundred seventy-five".