21637968665568 has 192 divisors, whose sum is σ = 57220197914880. Its totient is φ = 7159514959872.

The previous prime is 21637968665563. The next prime is 21637968665591. The reversal of 21637968665568 is 86556686973612.

It is a Cunningham number, because it is equal to 4651663²-1.

It is a super-2 number, since 2×21637968665568² (a number of 27 digits) contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21637968665493 and 21637968665502.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21637968665563) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (29) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 10856982780 + ... + 10856984772.

It is an arithmetic number, because the mean of its divisors is an integer number (298021864140).

Almost surely, 2^{21637968665568} is an apocalyptic number.

It is an amenable number.

21637968665568 is an abundant number, since it is smaller than the sum of its proper divisors (35582229249312).

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

21637968665568 is a wasteful number, since it uses less digits than its factorization.

21637968665568 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3649 (or 3641 counting only the distinct ones).

The product of its digits is 4702924800, while the sum is 78.

The spelling of 21637968665568 in words is "twenty-one trillion, six hundred thirty-seven billion, nine hundred sixty-eight million, six hundred sixty-five thousand, five hundred sixty-eight".