81235728 has 180 divisors, whose sum is σ = 274273740. Its totient is φ = 22353408.

The previous prime is 81235727. The next prime is 81235751. The reversal of 81235728 is 82753218.

81235728 is a `hidden beast` number, since 81 + 2 + 3 + 572 + 8 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 48608784 + 32626944 = 6972^2 + 5712^2 .

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a junction number, because it is equal to n+sod(n) for n = 81235692 and 81235701.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81235723) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 204426 + ... + 204822.

It is an arithmetic number, because the mean of its divisors is an integer number (1523743).

Almost surely, 2^81235728 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 81235728, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (137136870).

81235728 is an abundant number, since it is smaller than the sum of its proper divisors (193038012).

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

81235728 is a wasteful number, since it uses less digits than its factorization.

81235728 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 454 (or 438 counting only the distinct ones).

The product of its digits is 26880, while the sum is 36.

The square root of 81235728 is about 9013.0864857717. The cubic root of 81235728 is about 433.0941912582.

The spelling of 81235728 in words is "eighty-one million, two hundred thirty-five thousand, seven hundred twenty-eight".