20564 has 12 divisors (see below), whose sum is σ = 37044. Its totient is φ = 9984.

The previous prime is 20563. The next prime is 20593. The reversal of 20564 is 46502.

20564 is an esthetic number in base 12, because in such base its adjacent digits differ by 1.

It can be written as a sum of positive squares in 2 ways, for example, as 12100 + 8464 = 110^2 + 92^2 .

It is a nialpdrome in base 12.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20563) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (5) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 164 + ... + 260.

It is an arithmetic number, because the mean of its divisors is an integer number (3087).

2²⁰⁵⁶⁴ is an apocalyptic number.

It is an amenable number.

20564 is a deficient number, since it is larger than the sum of its proper divisors (16480).

20564 is a wasteful number, since it uses less digits than its factorization.

20564 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 154 (or 152 counting only the distinct ones).

The product of its (nonzero) digits is 240, while the sum is 17.

The square root of 20564 is about 143.4015341619. The cubic root of 20564 is about 27.3969698462.

The spelling of 20564 in words is "twenty thousand, five hundred sixty-four".