21017181265920 has 1792 divisors, whose sum is σ = 89006086656000. Its totient is φ = 4603543289856.

The previous prime is 21017181265907. The next prime is 21017181265963. The reversal of 21017181265920 is 2956218171012.

21017181265920 is a `hidden beast` number, since 2 + 10 + 17 + 18 + 1 + 26 + 592 + 0 = 666.

It is a tau number, because it is divible by the number of its divisors (1792).

It is a super-2 number, since 2×21017181265920² (a number of 27 digits) contains 22 as substring.

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 127 ways as a sum of consecutive naturals, for example, 40185814779 + ... + 40185815301.

Almost surely, 2^{21017181265920} is an apocalyptic number.

21017181265920 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 21017181265920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (44503043328000).

21017181265920 is an abundant number, since it is smaller than the sum of its proper divisors (67988905390080).

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

21017181265920 is a wasteful number, since it uses less digits than its factorization.

21017181265920 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 778 (or 748 counting only the distinct ones).

The product of its (nonzero) digits is 120960, while the sum is 45.

The spelling of 21017181265920 in words is "twenty-one trillion, seventeen billion, one hundred eighty-one million, two hundred sixty-five thousand, nine hundred twenty".