28091565 has 24 divisors (see below), whose sum is σ = 51557688. Its totient is φ = 14100480.

The previous prime is 28091563. The next prime is 28091573. The reversal of 28091565 is 56519082.

It is a happy number.

28091565 is a `hidden beast` number, since 2 + 8 + 0 + 91 + 565 = 666.

It can be written as a sum of positive squares in 4 ways, for example, as 181476 + 27910089 = 426^2 + 5283^2 .

It is not a de Polignac number, because 28091565 - 2¹ = 28091563 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28091561) 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 23 ways as a sum of consecutive naturals, for example, 17596 + ... + 19125.

It is an arithmetic number, because the mean of its divisors is an integer number (2148237).

Almost surely, 2^28091565 is an apocalyptic number.

It is an amenable number.

28091565 is a deficient number, since it is larger than the sum of its proper divisors (23466123).

28091565 is a wasteful number, since it uses less digits than its factorization.

28091565 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 36749 (or 36746 counting only the distinct ones).

The product of its (nonzero) digits is 21600, while the sum is 36.

The square root of 28091565 is about 5300.1476394531. The cubic root of 28091565 is about 303.9895432980.

The spelling of 28091565 in words is "twenty-eight million, ninety-one thousand, five hundred sixty-five".