81804391 has 16 divisors (see below), whose sum is σ = 88339680. Its totient is φ = 75479040.

The previous prime is 81804377. The next prime is 81804403. The reversal of 81804391 is 19340818.

It is a happy number.

It is a cyclic number.

It is not a de Polignac number, because 81804391 - 2⁹ = 81803879 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81804341) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 242575 + ... + 242911.

It is an arithmetic number, because the mean of its divisors is an integer number (5521230).

Almost surely, 2^81804391 is an apocalyptic number.

81804391 is a deficient number, since it is larger than the sum of its proper divisors (6535289).

81804391 is a wasteful number, since it uses less digits than its factorization.

81804391 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 594.

The product of its (nonzero) digits is 6912, while the sum is 34.

The square root of 81804391 is about 9044.5779890496. The cubic root of 81804391 is about 434.1024183666.

The spelling of 81804391 in words is "eighty-one million, eight hundred four thousand, three hundred ninety-one".