81918312 has 64 divisors (see below), whose sum is σ = 235015680. Its totient is φ = 23308992.

The previous prime is 81918289. The next prime is 81918323. The reversal of 81918312 is 21381918.

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, 46683 + ... + 48405.

It is an arithmetic number, because the mean of its divisors is an integer number (3672120).

Almost surely, 2^81918312 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 81918312, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (117507840).

81918312 is an abundant number, since it is smaller than the sum of its proper divisors (153097368).

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

81918312 is a wasteful number, since it uses less digits than its factorization.

81918312 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2022 (or 2018 counting only the distinct ones).

The product of its digits is 3456, while the sum is 33.

The square root of 81918312 is about 9050.8735490007. The cubic root of 81918312 is about 434.3038356028.

The spelling of 81918312 in words is "eighty-one million, nine hundred eighteen thousand, three hundred twelve".