81685384 has 32 divisors (see below), whose sum is σ = 168422400. Its totient is φ = 36832320.

The previous prime is 81685369. The next prime is 81685399. The reversal of 81685384 is 48358618.

It is an interprime number because it is at equal distance from previous prime (81685369) and next prime (81685399).

It is a self number, because there is not a number n which added to its sum of digits gives 81685384.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 7522 + ... + 14830.

It is an arithmetic number, because the mean of its divisors is an integer number (5263200).

Almost surely, 2^81685384 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 81685384, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (84211200).

81685384 is an abundant number, since it is smaller than the sum of its proper divisors (86737016).

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

81685384 is a wasteful number, since it uses less digits than its factorization.

81685384 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7453 (or 7449 counting only the distinct ones).

The product of its digits is 184320, while the sum is 43.

The square root of 81685384 is about 9037.9966806810. The cubic root of 81685384 is about 433.8918090584.

The spelling of 81685384 in words is "eighty-one million, six hundred eighty-five thousand, three hundred eighty-four".