21188565653 has 4 divisors (see below), whose sum is σ = 21188856780. Its totient is φ = 21188274528.

The previous prime is 21188565649. The next prime is 21188565661. The reversal of 21188565653 is 35656588112.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 14256837604 + 6931728049 = 119402^2 + 83257^2 .

It is a cyclic number.

It is not a de Polignac number, because 21188565653 - 2² = 21188565649 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21188565623) by changing a digit.

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, 72563 + ... + 218271.

It is an arithmetic number, because the mean of its divisors is an integer number (5297214195).

Almost surely, 2^21188565653 is an apocalyptic number.

It is an amenable number.

21188565653 is a deficient number, since it is larger than the sum of its proper divisors (291127).

21188565653 is a wasteful number, since it uses less digits than its factorization.

21188565653 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 291126.

The product of its digits is 1728000, while the sum is 50.

The spelling of 21188565653 in words is "twenty-one billion, one hundred eighty-eight million, five hundred sixty-five thousand, six hundred fifty-three".