81855090 has 64 divisors (see below), whose sum is σ = 219784320. Its totient is φ = 21677760.

The previous prime is 81855079. The next prime is 81855113. The reversal of 81855090 is 9055818.

81855090 is a `hidden beast` number, since 8 + 18 + 550 + 90 = 666.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 41425 + ... + 43355.

It is an arithmetic number, because the mean of its divisors is an integer number (3434130).

Almost surely, 2^81855090 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81855090, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (109892160).

81855090 is an abundant number, since it is smaller than the sum of its proper divisors (137929230).

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

81855090 is a wasteful number, since it uses less digits than its factorization.

81855090 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2104 (or 2098 counting only the distinct ones).

The product of its (nonzero) digits is 14400, while the sum is 36.

The square root of 81855090 is about 9047.3802838170. The cubic root of 81855090 is about 434.1920794599.

The spelling of 81855090 in words is "eighty-one million, eight hundred fifty-five thousand, ninety".