28309 has 2 divisors, whose sum is σ = 28310. Its totient is φ = 28308.

The previous prime is 28307. The next prime is 28319. The reversal of 28309 is 90382.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 23409 + 4900 = 153^2 + 70^2 .

It is a cyclic number.

It is not a de Polignac number, because 28309 - 2¹ = 28307 is a prime.

Together with 28307, it forms a pair of twin primes.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 28309.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (28307) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 14154 + 14155.

It is an arithmetic number, because the mean of its divisors is an integer number (14155).

2²⁸³⁰⁹ is an apocalyptic number.

It is an amenable number.

28309 is a deficient number, since it is larger than the sum of its proper divisors (1).

28309 is an equidigital number, since it uses as much as digits as its factorization.

28309 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 432, while the sum is 22.

The square root of 28309 is about 168.2527860096. The cubic root of 28309 is about 30.4771844061.

The spelling of 28309 in words is "twenty-eight thousand, three hundred nine".