81772128 has 72 divisors (see below), whose sum is σ = 233415000. Its totient is φ = 27154944.

The previous prime is 81772123. The next prime is 81772129. The reversal of 81772128 is 82127718.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (72).

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 = 81772092 and 81772101.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81772123) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 143428 + ... + 143996.

It is an arithmetic number, because the mean of its divisors is an integer number (3241875).

Almost surely, 2^81772128 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 81772128, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (116707500).

81772128 is an abundant number, since it is smaller than the sum of its proper divisors (151642872).

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

81772128 is a wasteful number, since it uses less digits than its factorization.

81772128 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1084 (or 1073 counting only the distinct ones).

The product of its digits is 12544, while the sum is 36.

The square root of 81772128 is about 9042.7942584137. The cubic root of 81772128 is about 434.0453420175.

The spelling of 81772128 in words is "eighty-one million, seven hundred seventy-two thousand, one hundred twenty-eight".