20564989 has 2 divisors, whose sum is σ = 20564990. Its totient is φ = 20564988.

The previous prime is 20564987. The next prime is 20565001. The reversal of 20564989 is 98946502.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20548089 + 16900 = 4533^2 + 130^2 .

It is a cyclic number.

It is not a de Polignac number, because 20564989 - 2¹ = 20564987 is a prime.

Together with 20564987, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20564987) 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 as a sum of consecutive naturals, namely, 10282494 + 10282495.

It is an arithmetic number, because the mean of its divisors is an integer number (10282495).

Almost surely, 2^20564989 is an apocalyptic number.

It is an amenable number.

20564989 is a deficient number, since it is larger than the sum of its proper divisors (1).

20564989 is an equidigital number, since it uses as much as digits as its factorization.

20564989 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 155520, while the sum is 43.

The square root of 20564989 is about 4534.8637245236. The cubic root of 20564989 is about 273.9740904692.

The spelling of 20564989 in words is "twenty million, five hundred sixty-four thousand, nine hundred eighty-nine".