81728136 has 128 divisors (see below), whose sum is σ = 261734400. Its totient is φ = 23146560.

The previous prime is 81728123. The next prime is 81728137. The reversal of 81728136 is 63182718.

It is a super-3 number, since 3×81728136³ (a number of 25 digits) contains 333 as substring.

It is a hoax number, since the sum of its digits (36) coincides with the sum of the digits of its distinct prime factors.

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

It is a nude number because it is divisible by every one of its digits.

It is a self number, because there is not a number n which added to its sum of digits gives 81728136.

It is not an unprimeable number, because it can be changed into a prime (81728137) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 288651 + ... + 288933.

It is an arithmetic number, because the mean of its divisors is an integer number (2044800).

Almost surely, 2^81728136 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 81728136, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (130867200).

81728136 is an abundant number, since it is smaller than the sum of its proper divisors (180006264).

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

81728136 is a wasteful number, since it uses less digits than its factorization.

81728136 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 496 (or 486 counting only the distinct ones).

The product of its digits is 16128, while the sum is 36.

The square root of 81728136 is about 9040.3614971969. The cubic root of 81728136 is about 433.9674917428.

The spelling of 81728136 in words is "eighty-one million, seven hundred twenty-eight thousand, one hundred thirty-six".