28509207 has 4 divisors (see below), whose sum is σ = 38012280. Its totient is φ = 19006136.

The previous prime is 28509199. The next prime is 28509209. The reversal of 28509207 is 70290582.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 28509207 - 2³ = 28509199 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28509209) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 4751532 + ... + 4751537.

It is an arithmetic number, because the mean of its divisors is an integer number (9503070).

Almost surely, 2^28509207 is an apocalyptic number.

28509207 is a deficient number, since it is larger than the sum of its proper divisors (9503073).

28509207 is an equidigital number, since it uses as much as digits as its factorization.

28509207 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9503072.

The product of its (nonzero) digits is 10080, while the sum is 33.

The square root of 28509207 is about 5339.4013709404. The cubic root of 28509207 is about 305.4886264330.

Adding to 28509207 its reverse (70290582), we get a palindrome (98799789).

The spelling of 28509207 in words is "twenty-eight million, five hundred nine thousand, two hundred seven".