21665859168 has 192 divisors, whose sum is σ = 63358848000. Its totient is φ = 6450683904.

The previous prime is 21665859121. The next prime is 21665859179. The reversal of 21665859168 is 86195856612.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 2788473 + ... + 2796231.

It is an arithmetic number, because the mean of its divisors is an integer number (329994000).

Almost surely, 2^21665859168 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 21665859168, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (31679424000).

21665859168 is an abundant number, since it is smaller than the sum of its proper divisors (41692988832).

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

21665859168 is a wasteful number, since it uses less digits than its factorization.

21665859168 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7877 (or 7869 counting only the distinct ones).

The product of its digits is 6220800, while the sum is 57.

The spelling of 21665859168 in words is "twenty-one billion, six hundred sixty-five million, eight hundred fifty-nine thousand, one hundred sixty-eight".