81501728 has 144 divisors (see below), whose sum is σ = 210212352. Its totient is φ = 30412800.

The previous prime is 81501709. The next prime is 81501733. The reversal of 81501728 is 82710518.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (32).

It is a junction number, because it is equal to n+sod(n) for n = 81501694 and 81501703.

It is an unprimeable number.

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 23 ways as a sum of consecutive naturals, for example, 840176 + ... + 840272.

It is an arithmetic number, because the mean of its divisors is an integer number (1459808).

Almost surely, 2^81501728 is an apocalyptic number.

81501728 is a gapful number since it is divisible by the number (88) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81501728, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (105106176).

81501728 is an abundant number, since it is smaller than the sum of its proper divisors (128710624).

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

81501728 is a wasteful number, since it uses less digits than its factorization.

81501728 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 167 (or 148 counting only the distinct ones).

The product of its (nonzero) digits is 4480, while the sum is 32.

The square root of 81501728 is about 9027.8307471950. The cubic root of 81501728 is about 433.5663871948.

The spelling of 81501728 in words is "eighty-one million, five hundred one thousand, seven hundred twenty-eight".