21688561006500 has 192 divisors, whose sum is σ = 64884201258240. Its totient is φ = 5625553075200.

The previous prime is 21688561006477. The next prime is 21688561006507. The reversal of 21688561006500 is 560016588612.

It is a self number, because there is not a number n which added to its sum of digits gives 21688561006500.

It is not an unprimeable number, because it can be changed into a prime (21688561006507) by changing a digit.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 183479416 + ... + 183597584.

It is an arithmetic number, because the mean of its divisors is an integer number (337938548220).

Almost surely, 2^{21688561006500} is an apocalyptic number.

21688561006500 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21688561006500, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (32442100629120).

21688561006500 is an abundant number, since it is smaller than the sum of its proper divisors (43195640251740).

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

21688561006500 is a wasteful number, since it uses less digits than its factorization.

21688561006500 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 121535 (or 121523 counting only the distinct ones).

The product of its (nonzero) digits is 691200, while the sum is 48.

The spelling of 21688561006500 in words is "twenty-one trillion, six hundred eighty-eight billion, five hundred sixty-one million, six thousand, five hundred".