81591168 has 128 divisors (see below), whose sum is σ = 233539200. Its totient is φ = 25159680.

The previous prime is 81591157. The next prime is 81591199. The reversal of 81591168 is 86119518.

It is a tau number, because it is divible by the number of its divisors (128).

It is a Smith number, since the sum of its digits (39) coincides with the sum of the digits of its prime factors.

Its product of digits (17280) is a multiple of the sum of its prime divisors (288).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 386583 + ... + 386793.

It is an arithmetic number, because the mean of its divisors is an integer number (1824525).

Almost surely, 2^81591168 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 81591168, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (116769600).

81591168 is an abundant number, since it is smaller than the sum of its proper divisors (151948032).

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

81591168 is a wasteful number, since it uses less digits than its factorization.

81591168 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 300 (or 288 counting only the distinct ones).

The product of its digits is 17280, while the sum is 39.

The square root of 81591168 is about 9032.7829598635. The cubic root of 81591168 is about 433.7249278058.

The spelling of 81591168 in words is "eighty-one million, five hundred ninety-one thousand, one hundred sixty-eight".