28239209 has 2 divisors, whose sum is σ = 28239210. Its totient is φ = 28239208.

The previous prime is 28239191. The next prime is 28239259. The reversal of 28239209 is 90293282.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19829209 + 8410000 = 4453^2 + 2900^2 .

It is a cyclic number.

It is not a de Polignac number, because 28239209 - 2²⁴ = 11461993 is a prime.

It is not a weakly prime, because it can be changed into another prime (28239259) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 14119604 + 14119605.

It is an arithmetic number, because the mean of its divisors is an integer number (14119605).

Almost surely, 2^28239209 is an apocalyptic number.

It is an amenable number.

28239209 is a deficient number, since it is larger than the sum of its proper divisors (1).

28239209 is an equidigital number, since it uses as much as digits as its factorization.

28239209 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 15552, while the sum is 35.

The square root of 28239209 is about 5314.0576775191. The cubic root of 28239209 is about 304.5211836683.

The spelling of 28239209 in words is "twenty-eight million, two hundred thirty-nine thousand, two hundred nine".