28256309 has 4 divisors (see below), whose sum is σ = 28295904. Its totient is φ = 28216716.

The previous prime is 28256303. The next prime is 28256311. The reversal of 28256309 is 90365282.

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 a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-28256309 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28256303) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 18707 + ... + 20160.

It is an arithmetic number, because the mean of its divisors is an integer number (7073976).

Almost surely, 2^28256309 is an apocalyptic number.

It is an amenable number.

28256309 is a deficient number, since it is larger than the sum of its proper divisors (39595).

28256309 is an equidigital number, since it uses as much as digits as its factorization.

28256309 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 39594.

The product of its (nonzero) digits is 25920, while the sum is 35.

The square root of 28256309 is about 5315.6663740306. Note that the first 3 decimals coincide. The cubic root of 28256309 is about 304.5826379571.

The spelling of 28256309 in words is "twenty-eight million, two hundred fifty-six thousand, three hundred nine".