21663631663555 has 16 divisors (see below), whose sum is σ = 29751444910080. Its totient is φ = 14834400969312.

The previous prime is 21663631663469. The next prime is 21663631663571. The reversal of 21663631663555 is 55536613636612.

It is a cyclic number.

It is not a de Polignac number, because 21663631663555 - 2⁹ = 21663631663043 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21663631663555.

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, 430406619 + ... + 430456948.

It is an arithmetic number, because the mean of its divisors is an integer number (1859465306880).

Almost surely, 2^{21663631663555} is an apocalyptic number.

21663631663555 is a deficient number, since it is larger than the sum of its proper divisors (8087813246525).

21663631663555 is an equidigital number, since it uses as much as digits as its factorization.

21663631663555 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 860864298.

The product of its digits is 52488000, while the sum is 58.

The spelling of 21663631663555 in words is "twenty-one trillion, six hundred sixty-three billion, six hundred thirty-one million, six hundred sixty-three thousand, five hundred fifty-five".