81558320 has 20 divisors (see below), whose sum is σ = 189623280. Its totient is φ = 32623296.

The previous prime is 81558319. The next prime is 81558329. The reversal of 81558320 is 2385518.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (20).

It is a super-2 number, since 2×81558320² = 13303519122444800, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (81558329) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 509660 + ... + 509819.

It is an arithmetic number, because the mean of its divisors is an integer number (9481164).

Almost surely, 2^81558320 is an apocalyptic number.

81558320 is a gapful number since it is divisible by the number (80) formed by its first and last digit.

It is an amenable number.

81558320 is an abundant number, since it is smaller than the sum of its proper divisors (108064960).

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

81558320 is a wasteful number, since it uses less digits than its factorization.

81558320 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1019492 (or 1019486 counting only the distinct ones).

The product of its (nonzero) digits is 9600, while the sum is 32.

The square root of 81558320 is about 9030.9645110586. The cubic root of 81558320 is about 433.6667151785. Note that the first 3 decimals are identical.

The spelling of 81558320 in words is "eighty-one million, five hundred fifty-eight thousand, three hundred twenty".