28565639 has 4 divisors (see below), whose sum is σ = 28577040. Its totient is φ = 28554240.

The previous prime is 28565633. The next prime is 28565659. The reversal of 28565639 is 93656582.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 93656582 = 2 ⋅46828291.

It is a cyclic number.

It is not a de Polignac number, because 28565639 - 2¹⁶ = 28500103 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 28565639.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28565633) 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, 122 + ... + 7559.

It is an arithmetic number, because the mean of its divisors is an integer number (7144260).

Almost surely, 2^28565639 is an apocalyptic number.

28565639 is a deficient number, since it is larger than the sum of its proper divisors (11401).

28565639 is an equidigital number, since it uses as much as digits as its factorization.

28565639 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11400.

The product of its digits is 388800, while the sum is 44.

The square root of 28565639 is about 5344.6832459932. The cubic root of 28565639 is about 305.6900581081.

Adding to 28565639 its reverse (93656582), we get a palindrome (122222221).

The spelling of 28565639 in words is "twenty-eight million, five hundred sixty-five thousand, six hundred thirty-nine".