81728031 has 24 divisors (see below), whose sum is σ = 138288384. Its totient is φ = 42455280.

The previous prime is 81728021. The next prime is 81728033. The reversal of 81728031 is 13082718.

It is a happy number.

It is not a de Polignac number, because 81728031 - 2⁶ = 81727967 is a prime.

It is a super-2 number, since 2×81728031² = 13358942102273922, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 81728031.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81728033) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 23655 + ... + 26888.

It is an arithmetic number, because the mean of its divisors is an integer number (5762016).

Almost surely, 2^81728031 is an apocalyptic number.

81728031 is a deficient number, since it is larger than the sum of its proper divisors (56560353).

81728031 is a wasteful number, since it uses less digits than its factorization.

81728031 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 50571 (or 50564 counting only the distinct ones).

The product of its (nonzero) digits is 2688, while the sum is 30.

The square root of 81728031 is about 9040.3556899051. The cubic root of 81728031 is about 433.9673058965.

The spelling of 81728031 in words is "eighty-one million, seven hundred twenty-eight thousand, thirty-one".