20556470021 has 4 divisors (see below), whose sum is σ = 20556916332. Its totient is φ = 20556023712.

The previous prime is 20556469981. The next prime is 20556470069. The reversal of 20556470021 is 12007465502.

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

It can be written as a sum of positive squares in 2 ways, for example, as 19123847521 + 1432622500 = 138289^2 + 37850^2 .

It is a cyclic number.

It is not a de Polignac number, because 20556470021 - 2⁶ = 20556469957 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 20556470021.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20556470821) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 144926 + ... + 249231.

It is an arithmetic number, because the mean of its divisors is an integer number (5139229083).

Almost surely, 2^20556470021 is an apocalyptic number.

It is an amenable number.

20556470021 is a deficient number, since it is larger than the sum of its proper divisors (446311).

20556470021 is an equidigital number, since it uses as much as digits as its factorization.

20556470021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 446310.

The product of its (nonzero) digits is 16800, while the sum is 32.

The spelling of 20556470021 in words is "twenty billion, five hundred fifty-six million, four hundred seventy thousand, twenty-one".