20904563 has 4 divisors (see below), whose sum is σ = 21625440. Its totient is φ = 20183688.

The previous prime is 20904511. The next prime is 20904589. The reversal of 20904563 is 36540902.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20904563 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (29), and also a Moran number because the ratio is a prime number: 720847 = 20904563 / (2 + 0 + 9 + 0 + 4 + 5 + 6 + 3).

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20909563) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 360395 + ... + 360452.

It is an arithmetic number, because the mean of its divisors is an integer number (5406360).

Almost surely, 2^20904563 is an apocalyptic number.

20904563 is a deficient number, since it is larger than the sum of its proper divisors (720877).

20904563 is an equidigital number, since it uses as much as digits as its factorization.

20904563 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 720876.

The product of its (nonzero) digits is 6480, while the sum is 29.

The square root of 20904563 is about 4572.1508067867. The cubic root of 20904563 is about 275.4738409269.

The spelling of 20904563 in words is "twenty million, nine hundred four thousand, five hundred sixty-three".