21561048415872 has 1536 divisors, whose sum is σ = 79631896780800. Its totient is φ = 5670025297920.

The previous prime is 21561048415871. The next prime is 21561048415889. The reversal of 21561048415872 is 27851484016512.

21561048415872 is a `hidden beast` number, since 2 + 1 + 5 + 6 + 1 + 0 + 484 + 158 + 7 + 2 = 666.

It is a Harshad number since it is a multiple of its sum of digits (54).

It is not an unprimeable number, because it can be changed into a prime (21561048415871) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 191 ways as a sum of consecutive naturals, for example, 33636580672 + ... + 33636581312.

It is an arithmetic number, because the mean of its divisors is an integer number (51843682800).

Almost surely, 2^{21561048415872} 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 21561048415872, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (39815948390400).

21561048415872 is an abundant number, since it is smaller than the sum of its proper divisors (58070848364928).

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

21561048415872 is a wasteful number, since it uses less digits than its factorization.

21561048415872 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 916 (or 892 counting only the distinct ones).

The product of its (nonzero) digits is 4300800, while the sum is 54.

The spelling of 21561048415872 in words is "twenty-one trillion, five hundred sixty-one billion, forty-eight million, four hundred fifteen thousand, eight hundred seventy-two".