20818865 has 4 divisors (see below), whose sum is σ = 24982644. Its totient is φ = 16655088.

The previous prime is 20818859. The next prime is 20818867. The reversal of 20818865 is 56881802.

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 5271616 + 15547249 = 2296^2 + 3943^2 .

It is a cyclic number.

It is not a de Polignac number, because 20818865 - 2¹² = 20814769 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (20818867) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2081882 + ... + 2081891.

It is an arithmetic number, because the mean of its divisors is an integer number (6245661).

Almost surely, 2^20818865 is an apocalyptic number.

It is an amenable number.

20818865 is a deficient number, since it is larger than the sum of its proper divisors (4163779).

20818865 is an equidigital number, since it uses as much as digits as its factorization.

20818865 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4163778.

The product of its (nonzero) digits is 30720, while the sum is 38.

The square root of 20818865 is about 4562.7694440986. The cubic root of 20818865 is about 275.0968914778.

The spelling of 20818865 in words is "twenty million, eight hundred eighteen thousand, eight hundred sixty-five".