21185168256 has 384 divisors, whose sum is σ = 76988620800. Its totient is φ = 5448351744.

The previous prime is 21185168219. The next prime is 21185168281. The reversal of 21185168256 is 65286158112.

21185168256 is a `hidden beast` number, since 2 + 1 + 1 + 8 + 516 + 82 + 56 = 666.

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

It is a super-2 number, since 2×21185168256² (a number of 21 digits) contains 22 as substring.

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, 3149665 + ... + 3156383.

It is an arithmetic number, because the mean of its divisors is an integer number (200491200).

Almost surely, 2^21185168256 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21185168256, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (38494310400).

21185168256 is an abundant number, since it is smaller than the sum of its proper divisors (55803452544).

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

21185168256 is a wasteful number, since it uses less digits than its factorization.

21185168256 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6786 (or 6771 counting only the distinct ones).

The product of its digits is 230400, while the sum is 45.

The spelling of 21185168256 in words is "twenty-one billion, one hundred eighty-five million, one hundred sixty-eight thousand, two hundred fifty-six".