309728 has 12 divisors (see below), whose sum is σ = 609840. Its totient is φ = 154848.

The previous prime is 309713. The next prime is 309731. The reversal of 309728 is 827903.

It is a self number, because there is not a number n which added to its sum of digits gives 309728.

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 309728.

It is an unprimeable number.

309728 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 as a sum of consecutive naturals, namely, 4808 + ... + 4871.

It is an arithmetic number, because the mean of its divisors is an integer number (50820).

2³⁰⁹⁷²⁸ is an apocalyptic number.

It is an amenable number.

309728 is a deficient number, since it is larger than the sum of its proper divisors (300112).

309728 is an equidigital number, since it uses as much as digits as its factorization.

309728 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9689 (or 9681 counting only the distinct ones).

The product of its (nonzero) digits is 3024, while the sum is 29.

The square root of 309728 is about 556.5321194684. The cubic root of 309728 is about 67.6591944424.

It can be divided in two parts, 3097 and 28, that added together give a 5-th power (3125 = 5⁵).

The spelling of 309728 in words is "three hundred nine thousand, seven hundred twenty-eight".