21655591999968 has 96 divisors (see below), whose sum is σ = 57143789176320. Its totient is φ = 7180719096320.

The previous prime is 21655591999949. The next prime is 21655592000011. The reversal of 21655591999968 is 86999919555612.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (96).

It is a super-2 number, since 2×21655591999968² (a number of 27 digits) contains 22 as substring.

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 15 ways as a sum of consecutive naturals, for example, 120171373 + ... + 120351443.

It is an arithmetic number, because the mean of its divisors is an integer number (595247803920).

Almost surely, 2^{21655591999968} is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21655591999968, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28571894588160).

21655591999968 is an abundant number, since it is smaller than the sum of its proper divisors (35488197176352).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21655591999968 is a wasteful number, since it uses less digits than its factorization.

21655591999968 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 186640 (or 186632 counting only the distinct ones).

The product of its digits is 4251528000, while the sum is 84.

The spelling of 21655591999968 in words is "twenty-one trillion, six hundred fifty-five billion, five hundred ninety-one million, nine hundred ninety-nine thousand, nine hundred sixty-eight".