21666666560 has 168 divisors, whose sum is σ = 64812793920. Its totient is φ = 6753162240.

The previous prime is 21666666559. The next prime is 21666666589. The reversal of 21666666560 is 6566666612.

It is a junction number, because it is equal to n+sod(n) for n = 21666666499 and 21666666508.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 231071 + ... + 311009.

It is an arithmetic number, because the mean of its divisors is an integer number (385790440).

Almost surely, 2^21666666560 is an apocalyptic number.

21666666560 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 21666666560, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (32406396960).

21666666560 is an abundant number, since it is smaller than the sum of its proper divisors (43146127360).

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

21666666560 is a wasteful number, since it uses less digits than its factorization.

21666666560 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 79985 (or 79964 counting only the distinct ones).

The product of its (nonzero) digits is 2799360, while the sum is 50.

The spelling of 21666666560 in words is "twenty-one billion, six hundred sixty-six million, six hundred sixty-six thousand, five hundred sixty".