28643665 has 4 divisors (see below), whose sum is σ = 34372404. Its totient is φ = 22914928.

The previous prime is 28643653. The next prime is 28643669. The reversal of 28643665 is 56634682.

It is a happy number.

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 6431296 + 22212369 = 2536^2 + 4713^2 .

It is a cyclic number.

It is not a de Polignac number, because 28643665 - 2¹⁷ = 28512593 is a prime.

It is a Smith number, since the sum of its digits (40) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (28643669) 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, 2864362 + ... + 2864371.

It is an arithmetic number, because the mean of its divisors is an integer number (8593101).

Almost surely, 2^28643665 is an apocalyptic number.

It is an amenable number.

28643665 is a deficient number, since it is larger than the sum of its proper divisors (5728739).

28643665 is an equidigital number, since it uses as much as digits as its factorization.

28643665 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5728738.

The product of its digits is 207360, while the sum is 40.

The square root of 28643665 is about 5351.9776718518. The cubic root of 28643665 is about 305.9681321563.

The spelling of 28643665 in words is "twenty-eight million, six hundred forty-three thousand, six hundred sixty-five".