81864590 has 16 divisors (see below), whose sum is σ = 153763488. Its totient is φ = 31322016.

The previous prime is 81864547. The next prime is 81864637. The reversal of 81864590 is 9546818.

It is a super-2 number, since 2×81864590² = 13403622191736200, which contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

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 7 ways as a sum of consecutive naturals, for example, 177737 + ... + 178196.

It is an arithmetic number, because the mean of its divisors is an integer number (9610218).

Almost surely, 2^81864590 is an apocalyptic number.

81864590 is a deficient number, since it is larger than the sum of its proper divisors (71898898).

81864590 is a wasteful number, since it uses less digits than its factorization.

81864590 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 355963.

The product of its (nonzero) digits is 69120, while the sum is 41.

The square root of 81864590 is about 9047.9052824397. The cubic root of 81864590 is about 434.2088760745.

The spelling of 81864590 in words is "eighty-one million, eight hundred sixty-four thousand, five hundred ninety".