81918924 has 24 divisors (see below), whose sum is σ = 191294208. Its totient is φ = 27284880.

The previous prime is 81918917. The next prime is 81918929. The reversal of 81918924 is 42981918.

It is not an unprimeable number, because it can be changed into a prime (81918929) 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, 23409 + ... + 26679.

It is an arithmetic number, because the mean of its divisors is an integer number (7970592).

Almost surely, 2^81918924 is an apocalyptic number.

It is an amenable number.

81918924 is an abundant number, since it is smaller than the sum of its proper divisors (109375284).

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

81918924 is a wasteful number, since it uses less digits than its factorization.

81918924 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5365 (or 5363 counting only the distinct ones).

The product of its digits is 41472, while the sum is 42.

The square root of 81918924 is about 9050.9073578288. The cubic root of 81918924 is about 434.3049171408.

The spelling of 81918924 in words is "eighty-one million, nine hundred eighteen thousand, nine hundred twenty-four".