21118820564 has 6 divisors (see below), whose sum is σ = 36957935994. Its totient is φ = 10559410280.

The previous prime is 21118820561. The next prime is 21118820573. The reversal of 21118820564 is 46502881112.

It can be written as a sum of positive squares in only one way, i.e., 15242371600 + 5876448964 = 123460^2 + 76658^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21118820561) 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, 2639852567 + ... + 2639852574.

It is an arithmetic number, because the mean of its divisors is an integer number (6159655999).

Almost surely, 2^21118820564 is an apocalyptic number.

It is an amenable number.

21118820564 is a deficient number, since it is larger than the sum of its proper divisors (15839115430).

21118820564 is a wasteful number, since it uses less digits than its factorization.

21118820564 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5279705145 (or 5279705143 counting only the distinct ones).

The product of its (nonzero) digits is 30720, while the sum is 38.

The spelling of 21118820564 in words is "twenty-one billion, one hundred eighteen million, eight hundred twenty thousand, five hundred sixty-four".