21556406616 has 64 divisors (see below), whose sum is σ = 54840240000. Its totient is φ = 7059065856.

The previous prime is 21556406581. The next prime is 21556406681. The reversal of 21556406616 is 61660465512.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 2670795 + ... + 2678853.

It is an arithmetic number, because the mean of its divisors is an integer number (856878750).

Almost surely, 2^21556406616 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 21556406616, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27420120000).

21556406616 is an abundant number, since it is smaller than the sum of its proper divisors (33283833384).

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

21556406616 is a wasteful number, since it uses less digits than its factorization.

21556406616 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10016 (or 10012 counting only the distinct ones).

The product of its (nonzero) digits is 259200, while the sum is 42.

The spelling of 21556406616 in words is "twenty-one billion, five hundred fifty-six million, four hundred six thousand, six hundred sixteen".