81857412 has 96 divisors (see below), whose sum is σ = 261228800. Its totient is φ = 21586176.

The previous prime is 81857411. The next prime is 81857417. The reversal of 81857412 is 21475818.

81857412 is a `hidden beast` number, since 81 + 8 + 574 + 1 + 2 = 666.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is not an unprimeable number, because it can be changed into a prime (81857411) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 5664 + ... + 13992.

Almost surely, 2^81857412 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81857412, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (130614400).

81857412 is an abundant number, since it is smaller than the sum of its proper divisors (179371388).

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

81857412 is a wasteful number, since it uses less digits than its factorization.

81857412 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8362 (or 8354 counting only the distinct ones).

The product of its digits is 17920, while the sum is 36.

The square root of 81857412 is about 9047.5086073460. The cubic root of 81857412 is about 434.1961850261.

The spelling of 81857412 in words is "eighty-one million, eight hundred fifty-seven thousand, four hundred twelve".