20205665 has 4 divisors (see below), whose sum is σ = 24246804. Its totient is φ = 16164528.

The previous prime is 20205623. The next prime is 20205697. The reversal of 20205665 is 56650202.

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 5058001 + 15147664 = 2249^2 + 3892^2 .

It is a cyclic number.

It is not a de Polignac number, because 20205665 - 2¹⁰ = 20204641 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2020562 + ... + 2020571.

It is an arithmetic number, because the mean of its divisors is an integer number (6061701).

Almost surely, 2^20205665 is an apocalyptic number.

It is an amenable number.

20205665 is a deficient number, since it is larger than the sum of its proper divisors (4041139).

20205665 is an equidigital number, since it uses as much as digits as its factorization.

20205665 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4041138.

The product of its (nonzero) digits is 3600, while the sum is 26.

The square root of 20205665 is about 4495.0711896476. The cubic root of 20205665 is about 272.3690249574.

Adding to 20205665 its reverse (56650202), we get a palindrome (76855867).

The spelling of 20205665 in words is "twenty million, two hundred five thousand, six hundred sixty-five".