1991728 has 20 divisors (see below), whose sum is σ = 3881448. Its totient is φ = 990080.

The previous prime is 1991723. The next prime is 1991729. The reversal of 1991728 is 8271991.

It is not an unprimeable number, because it can be changed into a prime (1991723) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 4275 + ... + 4717.

2^1991728 is an apocalyptic number.

It is an amenable number.

1991728 is a deficient number, since it is larger than the sum of its proper divisors (1889720).

1991728 is a wasteful number, since it uses less digits than its factorization.

1991728 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 732 (or 726 counting only the distinct ones).

The product of its digits is 9072, while the sum is 37.

The square root of 1991728 is about 1411.2859384264. The cubic root of 1991728 is about 125.8181638464.

The spelling of 1991728 in words is "one million, nine hundred ninety-one thousand, seven hundred twenty-eight".