20643816560555 has 4 divisors (see below), whose sum is σ = 24772579872672. Its totient is φ = 16515053248440.

The previous prime is 20643816560531. The next prime is 20643816560569. The reversal of 20643816560555 is 55506561834602.

It is a happy number.

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

It is not a de Polignac number, because 20643816560555 - 2¹⁸ = 20643816298411 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 20643816560555.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2064381656051 + ... + 2064381656060.

It is an arithmetic number, because the mean of its divisors is an integer number (6193144968168).

Almost surely, 2^{20643816560555} is an apocalyptic number.

20643816560555 is a deficient number, since it is larger than the sum of its proper divisors (4128763312117).

20643816560555 is an equidigital number, since it uses as much as digits as its factorization.

20643816560555 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4128763312116.

The product of its (nonzero) digits is 25920000, while the sum is 56.

The spelling of 20643816560555 in words is "twenty trillion, six hundred forty-three billion, eight hundred sixteen million, five hundred sixty thousand, five hundred fifty-five".