21189055680 has 896 divisors, whose sum is σ = 86917743360. Its totient is φ = 4873125888.

The previous prime is 21189055651. The next prime is 21189055687. The reversal of 21189055680 is 8655098112.

It is a happy number.

21189055680 is a `hidden beast` number, since 2 + 1 + 1 + 8 + 90 + 556 + 8 + 0 = 666.

It is a super-2 number, since 2×21189055680² (a number of 21 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is not an unprimeable number, because it can be changed into a prime (21189055687) 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 127 ways as a sum of consecutive naturals, for example, 154664572 + ... + 154664708.

It is an arithmetic number, because the mean of its divisors is an integer number (97006410).

Almost surely, 2^21189055680 is an apocalyptic number.

21189055680 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 21189055680, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (43458871680).

21189055680 is an abundant number, since it is smaller than the sum of its proper divisors (65728687680).

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

21189055680 is a wasteful number, since it uses less digits than its factorization.

21189055680 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 205 (or 177 counting only the distinct ones).

The product of its (nonzero) digits is 172800, while the sum is 45.

The spelling of 21189055680 in words is "twenty-one billion, one hundred eighty-nine million, fifty-five thousand, six hundred eighty".