81857475 has 36 divisors (see below), whose sum is σ = 167564176. Its totient is φ = 37419840.

The previous prime is 81857473. The next prime is 81857513. The reversal of 81857475 is 57475818.

It is a happy number.

81857475 is a `hidden beast` number, since 8 + 1 + 8 + 574 + 75 = 666.

It is not a de Polignac number, because 81857475 - 2¹ = 81857473 is a prime.

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

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 81857475.

It is not an unprimeable number, because it can be changed into a prime (81857473) by changing a digit.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 24412 + ... + 27561.

Almost surely, 2^81857475 is an apocalyptic number.

81857475 is an abundant number, since it is smaller than the sum of its proper divisors (85706701).

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

81857475 is a wasteful number, since it uses less digits than its factorization.

81857475 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 51996 (or 51988 counting only the distinct ones).

The product of its digits is 313600, while the sum is 45.

The square root of 81857475 is about 9047.5120889668. The cubic root of 81857475 is about 434.1962964164.

The spelling of 81857475 in words is "eighty-one million, eight hundred fifty-seven thousand, four hundred seventy-five".