20318561 has 4 divisors (see below), whose sum is σ = 20331312. Its totient is φ = 20305812.

The previous prime is 20318549. The next prime is 20318579. The reversal of 20318561 is 16581302.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20318561 is a prime.

It is a super-2 number, since 2×20318561² = 825687842221442, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 20318561.

It is not an unprimeable number, because it can be changed into a prime (20318521) 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, 3575 + ... + 7308.

It is an arithmetic number, because the mean of its divisors is an integer number (5082828).

Almost surely, 2^20318561 is an apocalyptic number.

It is an amenable number.

20318561 is a deficient number, since it is larger than the sum of its proper divisors (12751).

20318561 is a wasteful number, since it uses less digits than its factorization.

20318561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12750.

The product of its (nonzero) digits is 1440, while the sum is 26.

The square root of 20318561 is about 4507.6114517558. The cubic root of 20318561 is about 272.8753562501.

Adding to 20318561 its reverse (16581302), we get a palindrome (36899863).

The spelling of 20318561 in words is "twenty million, three hundred eighteen thousand, five hundred sixty-one".