21655563120 has 240 divisors, whose sum is σ = 77700205440. Its totient is φ = 5388996096.

The previous prime is 21655563113. The next prime is 21655563191. The reversal of 21655563120 is 2136555612.

21655563120 is a `hidden beast` number, since 2 + 16 + 5 + 5 + 5 + 631 + 2 + 0 = 666.

It is a tau number, because it is divible by the number of its divisors (240).

It is a Harshad number since it is a multiple of its sum of digits (36).

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, 904747 + ... + 928373.

It is an arithmetic number, because the mean of its divisors is an integer number (323750856).

Almost surely, 2^21655563120 is an apocalyptic number.

21655563120 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 21655563120, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (38850102720).

21655563120 is an abundant number, since it is smaller than the sum of its proper divisors (56044642320).

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

21655563120 is a wasteful number, since it uses less digits than its factorization.

21655563120 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 23732 (or 23723 counting only the distinct ones).

The product of its (nonzero) digits is 54000, while the sum is 36.

The spelling of 21655563120 in words is "twenty-one billion, six hundred fifty-five million, five hundred sixty-three thousand, one hundred twenty".