81865808 has 40 divisors (see below), whose sum is σ = 163287168. Its totient is φ = 39739392.

The previous prime is 81865801. The next prime is 81865831. The reversal of 81865808 is 80856818.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81865801) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 176585 + ... + 177047.

Almost surely, 2^81865808 is an apocalyptic number.

It is an amenable number.

81865808 is a deficient number, since it is larger than the sum of its proper divisors (81421360).

81865808 is a wasteful number, since it uses less digits than its factorization.

81865808 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 771 (or 765 counting only the distinct ones).

The product of its (nonzero) digits is 122880, while the sum is 44.

The square root of 81865808 is about 9047.9725905862. The cubic root of 81865808 is about 434.2110294833.

The spelling of 81865808 in words is "eighty-one million, eight hundred sixty-five thousand, eight hundred eight".