21561330722724 has 243 divisors, whose sum is σ = 60094036299843. Its totient is φ = 6515346958848.

The previous prime is 21561330722719. The next prime is 21561330722731. The reversal of 21561330722724 is 42722703316512.

The square root of 21561330722724 is 4643418.

It is a perfect power (a square), and thus also a powerful number.

21561330722724 is a `hidden beast` number, since 2 + 1 + 5 + 613 + 3 + 0 + 7 + 2 + 2 + 7 + 24 = 666.

It can be written as a sum of positive squares in 4 ways, for example, as 6650673632100 + 14910657090624 = 2578890^2 + 3861432^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 21561330722724.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 80 ways as a sum of consecutive naturals, for example, 21369009132 + ... + 21369010140.

Almost surely, 2^{21561330722724} is an apocalyptic number.

21561330722724 is the 4643418-th square number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21561330722724

21561330722724 is an abundant number, since it is smaller than the sum of its proper divisors (38532705577119).

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

21561330722724 is a wasteful number, since it uses less digits than its factorization.

21561330722724 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2172 (or 1086 counting only the distinct ones).

The product of its (nonzero) digits is 846720, while the sum is 45.

The spelling of 21561330722724 in words is "twenty-one trillion, five hundred sixty-one billion, three hundred thirty million, seven hundred twenty-two thousand, seven hundred twenty-four".