20564355621 has 16 divisors (see below), whose sum is σ = 27885461760. Its totient is φ = 13477900800.

The previous prime is 20564355613. The next prime is 20564355629. The reversal of 20564355621 is 12655346502.

It is an interprime number because it is at equal distance from previous prime (20564355613) and next prime (20564355629).

It is not a de Polignac number, because 20564355621 - 2³ = 20564355613 is a prime.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 20564355621.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20564355629) 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 15 ways as a sum of consecutive naturals, for example, 130980 + ... + 241421.

It is an arithmetic number, because the mean of its divisors is an integer number (1742841360).

Almost surely, 2^20564355621 is an apocalyptic number.

It is an amenable number.

20564355621 is a deficient number, since it is larger than the sum of its proper divisors (7321106139).

20564355621 is a wasteful number, since it uses less digits than its factorization.

20564355621 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 372716.

The product of its (nonzero) digits is 216000, while the sum is 39.

The spelling of 20564355621 in words is "twenty billion, five hundred sixty-four million, three hundred fifty-five thousand, six hundred twenty-one".