991728 has 60 divisors (see below), whose sum is σ = 2843568. Its totient is φ = 322560.

The previous prime is 991723. The next prime is 991733. The reversal of 991728 is 827199.

It is a happy number.

991728 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is an interprime number because it is at equal distance from previous prime (991723) and next prime (991733).

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 = 991692 and 991701.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 991728.

It is not an unprimeable number, because it can be changed into a prime (991723) by changing a digit.

991728 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 10176 + ... + 10272.

2⁹⁹¹⁷²⁸ 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 991728, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1421784).

991728 is an abundant number, since it is smaller than the sum of its proper divisors (1851840).

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

991728 is a wasteful number, since it uses less digits than its factorization.

991728 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 182 (or 173 counting only the distinct ones).

The product of its digits is 9072, while the sum is 36.

The square root of 991728 is about 995.8554111918. The cubic root of 991728 is about 99.7235028646.

The spelling of 991728 in words is "nine hundred ninety-one thousand, seven hundred twenty-eight".