28904509 has 4 divisors (see below), whose sum is σ = 28923804. Its totient is φ = 28885216.

The previous prime is 28904443. The next prime is 28904521. The reversal of 28904509 is 90540982.

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

It can be written as a sum of positive squares in 2 ways, for example, as 1968409 + 26936100 = 1403^2 + 5190^2 .

It is a cyclic number.

It is not a de Polignac number, because 28904509 - 2¹³ = 28896317 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 (28904009) 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, 7192 + ... + 10465.

It is an arithmetic number, because the mean of its divisors is an integer number (7230951).

Almost surely, 2^28904509 is an apocalyptic number.

It is an amenable number.

28904509 is a deficient number, since it is larger than the sum of its proper divisors (19295).

28904509 is a wasteful number, since it uses less digits than its factorization.

28904509 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 19294.

The product of its (nonzero) digits is 25920, while the sum is 37.

The square root of 28904509 is about 5376.2913797524. The cubic root of 28904509 is about 306.8940949731.

The spelling of 28904509 in words is "twenty-eight million, nine hundred four thousand, five hundred nine".