81868920 has 64 divisors (see below), whose sum is σ = 280696320. Its totient is φ = 18712704.

The previous prime is 81868909. The next prime is 81868951. The reversal of 81868920 is 2986818.

81868920 = T₂₃₆ + T₂₃₇ + ... + T₇₉₅.

It is a Harshad number since it is a multiple of its sum of digits (42).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 47892 + ... + 49571.

It is an arithmetic number, because the mean of its divisors is an integer number (4385880).

Almost surely, 2^81868920 is an apocalyptic number.

It is an amenable number.

81868920 is an abundant number, since it is smaller than the sum of its proper divisors (198827400).

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

81868920 is a wasteful number, since it uses less digits than its factorization.

81868920 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 97484 (or 97480 counting only the distinct ones).

The product of its (nonzero) digits is 55296, while the sum is 42.

The square root of 81868920 is about 9048.1445611794. The cubic root of 81868920 is about 434.2165313635.

The spelling of 81868920 in words is "eighty-one million, eight hundred sixty-eight thousand, nine hundred twenty".