21665564033615 has 4 divisors (see below), whose sum is σ = 25998676840344. Its totient is φ = 17332451226888.

The previous prime is 21665564033599. The next prime is 21665564033627. The reversal of 21665564033615 is 51633046556612.

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

It is a cyclic number.

It is not a de Polignac number, because 21665564033615 - 2⁴ = 21665564033599 is a prime.

It is a Duffinian number.

It is a congruent number.

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, 2166556403357 + ... + 2166556403366.

It is an arithmetic number, because the mean of its divisors is an integer number (6499669210086).

Almost surely, 2^{21665564033615} is an apocalyptic number.

21665564033615 is a deficient number, since it is larger than the sum of its proper divisors (4333112806729).

21665564033615 is an equidigital number, since it uses as much as digits as its factorization.

21665564033615 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4333112806728.

The product of its (nonzero) digits is 11664000, while the sum is 53.

The spelling of 21665564033615 in words is "twenty-one trillion, six hundred sixty-five billion, five hundred sixty-four million, thirty-three thousand, six hundred fifteen".