20565665 has 16 divisors (see below), whose sum is σ = 26247888. Its totient is φ = 15415296.

The previous prime is 20565659. The next prime is 20565667. The reversal of 20565665 is 56656502.

It can be written as a sum of positive squares in 8 ways, for example, as 5456896 + 15108769 = 2336^2 + 3887^2 .

It is a cyclic number.

It is not a de Polignac number, because 20565665 - 2²² = 16371361 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20565667) 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 15 ways as a sum of consecutive naturals, for example, 26219 + ... + 26991.

It is an arithmetic number, because the mean of its divisors is an integer number (1640493).

Almost surely, 2^20565665 is an apocalyptic number.

It is an amenable number.

20565665 is a deficient number, since it is larger than the sum of its proper divisors (5682223).

20565665 is a wasteful number, since it uses less digits than its factorization.

20565665 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1108.

The product of its (nonzero) digits is 54000, while the sum is 35.

The square root of 20565665 is about 4534.9382575731. The cubic root of 20565665 is about 273.9770924071.

The spelling of 20565665 in words is "twenty million, five hundred sixty-five thousand, six hundred sixty-five".