21617715456 has 432 divisors, whose sum is σ = 69907743360. Its totient is φ = 6642155520.

The previous prime is 21617715439. The next prime is 21617715461. The reversal of 21617715456 is 65451771612.

21617715456 is a `hidden beast` number, since 2 + 16 + 177 + 15 + 456 = 666.

It is a tau number, because it is divible by the number of its divisors (432).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 41492476 + ... + 41492996.

It is an arithmetic number, because the mean of its divisors is an integer number (161823480).

Almost surely, 2^21617715456 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 21617715456, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (34953871680).

21617715456 is an abundant number, since it is smaller than the sum of its proper divisors (48290027904).

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

21617715456 is an equidigital number, since it uses as much as digits as its factorization.

21617715456 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 604 (or 578 counting only the distinct ones).

The product of its digits is 352800, while the sum is 45.

The spelling of 21617715456 in words is "twenty-one billion, six hundred seventeen million, seven hundred fifteen thousand, four hundred fifty-six".