81535872 has 128 divisors (see below), whose sum is σ = 239904000. Its totient is φ = 24330240.

The previous prime is 81535847. The next prime is 81535877. The reversal of 81535872 is 27853518.

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

It is a self number, because there is not a number n which added to its sum of digits gives 81535872.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81535877) 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, 409629 + ... + 409827.

It is an arithmetic number, because the mean of its divisors is an integer number (1874250).

Almost surely, 2^81535872 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 81535872, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (119952000).

81535872 is an abundant number, since it is smaller than the sum of its proper divisors (158368128).

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

81535872 is a wasteful number, since it uses less digits than its factorization.

81535872 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 324 (or 312 counting only the distinct ones).

The product of its digits is 67200, while the sum is 39.

The square root of 81535872 is about 9029.7215903925. The cubic root of 81535872 is about 433.6269242505.

The spelling of 81535872 in words is "eighty-one million, five hundred thirty-five thousand, eight hundred seventy-two".