81558520 has 128 divisors (see below), whose sum is σ = 207152640. Its totient is φ = 28753920.

The previous prime is 81558461. The next prime is 81558523. The reversal of 81558520 is 2585518.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (34).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81558523) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 1117204 + ... + 1117276.

It is an arithmetic number, because the mean of its divisors is an integer number (1618380).

Almost surely, 2^81558520 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 81558520, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (103576320).

81558520 is an abundant number, since it is smaller than the sum of its proper divisors (125594120).

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

81558520 is a wasteful number, since it uses less digits than its factorization.

81558520 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 185 (or 181 counting only the distinct ones).

The product of its (nonzero) digits is 16000, while the sum is 34.

The square root of 81558520 is about 9030.9755840662. The cubic root of 81558520 is about 433.6670696621.

The spelling of 81558520 in words is "eighty-one million, five hundred fifty-eight thousand, five hundred twenty".