81551328 has 96 divisors (see below), whose sum is σ = 224824320. Its totient is φ = 25850880.

The previous prime is 81551321. The next prime is 81551333. The reversal of 81551328 is 82315518.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (96).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81551321) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 199188 + ... + 199596.

It is an arithmetic number, because the mean of its divisors is an integer number (2341920).

Almost surely, 2^81551328 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 81551328, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (112412160).

81551328 is an abundant number, since it is smaller than the sum of its proper divisors (143272992).

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

81551328 is a wasteful number, since it uses less digits than its factorization.

81551328 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 520 (or 512 counting only the distinct ones).

The product of its digits is 9600, while the sum is 33.

The square root of 81551328 is about 9030.5773901783. The cubic root of 81551328 is about 433.6543220659.

The spelling of 81551328 in words is "eighty-one million, five hundred fifty-one thousand, three hundred twenty-eight".