21688561006464 has 128 divisors (see below), whose sum is σ = 65014691472000. Its totient is φ = 6345660446720.

The previous prime is 21688561006447. The next prime is 21688561006477. The reversal of 21688561006464 is 46460016588612.

It is a tau number, because it is divible by the number of its divisors (128).

It is a super-2 number, since 2×21688561006464² (a number of 27 digits) contains 22 as substring.

It is a congruent 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, 88405134 + ... + 88650125.

It is an arithmetic number, because the mean of its divisors is an integer number (507927277125).

Almost surely, 2^{21688561006464} is an apocalyptic number.

21688561006464 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

21688561006464 is an abundant number, since it is smaller than the sum of its proper divisors (43326130465536).

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

21688561006464 is a wasteful number, since it uses less digits than its factorization.

21688561006464 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 177055316 (or 177055304 counting only the distinct ones).

The product of its (nonzero) digits is 13271040, while the sum is 57.

The spelling of 21688561006464 in words is "twenty-one trillion, six hundred eighty-eight billion, five hundred sixty-one million, six thousand, four hundred sixty-four".