21663865745 has 16 divisors (see below), whose sum is σ = 26948801088. Its totient is φ = 16705074240.

The previous prime is 21663865739. The next prime is 21663865763. The reversal of 21663865745 is 54756836612.

It is a happy number.

It is not a de Polignac number, because 21663865745 - 2¹⁸ = 21663603601 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 527411 + ... + 567000.

It is an arithmetic number, because the mean of its divisors is an integer number (1684300068).

Almost surely, 2^21663865745 is an apocalyptic number.

It is an amenable number.

21663865745 is a deficient number, since it is larger than the sum of its proper divisors (5284935343).

21663865745 is a wasteful number, since it uses less digits than its factorization.

21663865745 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1094560.

The product of its digits is 7257600, while the sum is 53.

The spelling of 21663865745 in words is "twenty-one billion, six hundred sixty-three million, eight hundred sixty-five thousand, seven hundred forty-five".