81801684 has 96 divisors (see below), whose sum is σ = 223534080. Its totient is φ = 25833600.

The previous prime is 81801677. The next prime is 81801697. The reversal of 81801684 is 48610818.

It is a Smith number, since the sum of its digits (36) coincides with the sum of the digits of its prime factors.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 177214 + ... + 177674.

It is an arithmetic number, because the mean of its divisors is an integer number (2328480).

Almost surely, 2^81801684 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 81801684, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (111767040).

81801684 is an abundant number, since it is smaller than the sum of its proper divisors (141732396).

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

81801684 is a wasteful number, since it uses less digits than its factorization.

81801684 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 558 (or 550 counting only the distinct ones).

The product of its (nonzero) digits is 12288, while the sum is 36.

The square root of 81801684 is about 9044.4283401440. The cubic root of 81801684 is about 434.0976300001.

The spelling of 81801684 in words is "eighty-one million, eight hundred one thousand, six hundred eighty-four".