28385809 has 4 divisors (see below), whose sum is σ = 29364660. Its totient is φ = 27406960.

The previous prime is 28385803. The next prime is 28385813. The reversal of 28385809 is 90858382.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 90858382 = 2 ⋅45429191.

It can be written as a sum of positive squares in 2 ways, for example, as 4717584 + 23668225 = 2172^2 + 4865^2 .

It is a cyclic number.

It is not a de Polignac number, because 28385809 - 2⁷ = 28385681 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (28385803) 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, 489382 + ... + 489439.

It is an arithmetic number, because the mean of its divisors is an integer number (7341165).

Almost surely, 2^28385809 is an apocalyptic number.

28385809 is a gapful number since it is divisible by the number (29) formed by its first and last digit.

It is an amenable number.

28385809 is a deficient number, since it is larger than the sum of its proper divisors (978851).

28385809 is an equidigital number, since it uses as much as digits as its factorization.

28385809 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 978850.

The product of its (nonzero) digits is 138240, while the sum is 43.

The square root of 28385809 is about 5327.8334245733. The cubic root of 28385809 is about 305.0472344654.

The spelling of 28385809 in words is "twenty-eight million, three hundred eighty-five thousand, eight hundred nine".