21161905756560 has 480 divisors, whose sum is σ = 78257753683200. Its totient is φ = 5296148250624.

The previous prime is 21161905756531. The next prime is 21161905756567. The reversal of 21161905756560 is 6565750916112.

It is a happy number.

21161905756560 is a `hidden beast` number, since 2 + 1 + 1 + 6 + 1 + 9 + 0 + 5 + 75 + 6 + 560 = 666.

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

It is a junction number, because it is equal to n+sod(n) for n = 21161905756497 and 21161905756506.

It is not an unprimeable number, because it can be changed into a prime (21161905756567) by changing a digit.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 116568741 + ... + 116750139.

It is an arithmetic number, because the mean of its divisors is an integer number (163036986840).

Almost surely, 2^{21161905756560} is an apocalyptic number.

21161905756560 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 21161905756560, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (39128876841600).

21161905756560 is an abundant number, since it is smaller than the sum of its proper divisors (57095847926640).

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

21161905756560 is a wasteful number, since it uses less digits than its factorization.

21161905756560 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 181797 (or 181779 counting only the distinct ones).

The product of its (nonzero) digits is 3402000, while the sum is 54.

The spelling of 21161905756560 in words is "twenty-one trillion, one hundred sixty-one billion, nine hundred five million, seven hundred fifty-six thousand, five hundred sixty".