20564209 has 2 divisors, whose sum is σ = 20564210. Its totient is φ = 20564208.

The previous prime is 20564207. The next prime is 20564279. The reversal of 20564209 is 90246502.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 10419984 + 10144225 = 3228^2 + 3185^2 .

It is a cyclic number.

It is not a de Polignac number, because 20564209 - 2¹ = 20564207 is a prime.

Together with 20564207, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (20564207) 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 as a sum of consecutive naturals, namely, 10282104 + 10282105.

It is an arithmetic number, because the mean of its divisors is an integer number (10282105).

Almost surely, 2^20564209 is an apocalyptic number.

It is an amenable number.

20564209 is a deficient number, since it is larger than the sum of its proper divisors (1).

20564209 is an equidigital number, since it uses as much as digits as its factorization.

20564209 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 4320, while the sum is 28.

The square root of 20564209 is about 4534.7777233289. Note that the first 4 decimals coincide. The cubic root of 20564209 is about 273.9706266131.

The spelling of 20564209 in words is "twenty million, five hundred sixty-four thousand, two hundred nine".