21681508408560 has 1440 divisors, whose sum is σ = 99795197698560. Its totient is φ = 4146760396800.

The previous prime is 21681508408531. The next prime is 21681508408561. The reversal of 21681508408560 is 6580480518612.

21681508408560 is a `hidden beast` number, since 2 + 1 + 6 + 81 + 508 + 4 + 0 + 8 + 56 + 0 = 666.

It is a junction number, because it is equal to n+sod(n) for n = 21681508408497 and 21681508408506.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21681508408561) by changing a digit.

It is a polite number, since it can be written in 287 ways as a sum of consecutive naturals, for example, 1811163375 + ... + 1811175345.

It is an arithmetic number, because the mean of its divisors is an integer number (69302220624).

Almost surely, 2^{21681508408560} is an apocalyptic number.

21681508408560 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 21681508408560, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (49897598849280).

21681508408560 is an abundant number, since it is smaller than the sum of its proper divisors (78113689290000).

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

21681508408560 is a wasteful number, since it uses less digits than its factorization.

21681508408560 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12387 (or 12371 counting only the distinct ones).

The product of its (nonzero) digits is 3686400, while the sum is 54.

The spelling of 21681508408560 in words is "twenty-one trillion, six hundred eighty-one billion, five hundred eight million, four hundred eight thousand, five hundred sixty".