21104666663 has 4 divisors (see below), whose sum is σ = 21109745280. Its totient is φ = 21099588048.

The previous prime is 21104666659. The next prime is 21104666699. The reversal of 21104666663 is 36666640112.

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 21104666663 - 2² = 21104666659 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 21104666663.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21104660663) 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, 2533070 + ... + 2541387.

It is an arithmetic number, because the mean of its divisors is an integer number (5277436320).

Almost surely, 2^21104666663 is an apocalyptic number.

21104666663 is a deficient number, since it is larger than the sum of its proper divisors (5078617).

21104666663 is an equidigital number, since it uses as much as digits as its factorization.

21104666663 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5078616.

The product of its (nonzero) digits is 186624, while the sum is 41.

The spelling of 21104666663 in words is "twenty-one billion, one hundred four million, six hundred sixty-six thousand, six hundred sixty-three".