21255101665920 has 384 divisors, whose sum is σ = 77510459295360. Its totient is φ = 5356268003328.

The previous prime is 21255101665871. The next prime is 21255101665939. The reversal of 21255101665920 is 2956610155212.

21255101665920 is a `hidden beast` number, since 2 + 1 + 2 + 5 + 51 + 0 + 1 + 6 + 6 + 592 + 0 = 666.

It is a tau number, because it is divible by the number of its divisors (384).

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

It is an unprimeable number.

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 47 ways as a sum of consecutive naturals, for example, 10029334 + ... + 11962346.

It is an arithmetic number, because the mean of its divisors is an integer number (201850154415).

Almost surely, 2^{21255101665920} is an apocalyptic number.

21255101665920 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 21255101665920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (38755229647680).

21255101665920 is an abundant number, since it is smaller than the sum of its proper divisors (56255357629440).

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

21255101665920 is a wasteful number, since it uses less digits than its factorization.

21255101665920 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1933144 (or 1933129 counting only the distinct ones).

The product of its (nonzero) digits is 324000, while the sum is 45.

The spelling of 21255101665920 in words is "twenty-one trillion, two hundred fifty-five billion, one hundred one million, six hundred sixty-five thousand, nine hundred twenty".