21561066362880 has 1344 divisors, whose sum is σ = 85901657587200. Its totient is φ = 5147597537280.

The previous prime is 21561066362879. The next prime is 21561066362909. The reversal of 21561066362880 is 8826366016512.

21561066362880 is a `hidden beast` number, since 2 + 1 + 5 + 6 + 1 + 0 + 6 + 6 + 3 + 628 + 8 + 0 = 666.

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

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 111 ways as a sum of consecutive naturals, for example, 5501673561 + ... + 5501677479.

It is an arithmetic number, because the mean of its divisors is an integer number (63914923800).

Almost surely, 2^{21561066362880} is an apocalyptic number.

21561066362880 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 21561066362880, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (42950828793600).

21561066362880 is an abundant number, since it is smaller than the sum of its proper divisors (64340591224320).

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

21561066362880 is an equidigital number, since it uses as much as digits as its factorization.

21561066362880 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4042 (or 4007 counting only the distinct ones).

The product of its (nonzero) digits is 4976640, while the sum is 54.

The spelling of 21561066362880 in words is "twenty-one trillion, five hundred sixty-one billion, sixty-six million, three hundred sixty-two thousand, eight hundred eighty".