28209 has 4 divisors (see below), whose sum is σ = 37616. Its totient is φ = 18804.

The previous prime is 28201. The next prime is 28211. The reversal of 28209 is 90282.

28209 is digitally balanced in base 4, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 28209 - 2³ = 28201 is a prime.

It is a D-number.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (28201) 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, 4699 + ... + 4704.

It is an arithmetic number, because the mean of its divisors is an integer number (9404).

2²⁸²⁰⁹ is an apocalyptic number.

It is an amenable number.

28209 is a deficient number, since it is larger than the sum of its proper divisors (9407).

28209 is an equidigital number, since it uses as much as digits as its factorization.

28209 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9406.

The product of its (nonzero) digits is 288, while the sum is 21.

The square root of 28209 is about 167.9553512098. The cubic root of 28209 is about 30.4412557364.

The spelling of 28209 in words is "twenty-eight thousand, two hundred nine".