21155164361256 has 256 divisors, whose sum is σ = 57535571635200. Its totient is φ = 6460619802624.

The previous prime is 21155164361173. The next prime is 21155164361311. The reversal of 21155164361256 is 65216346155112.

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 63 ways as a sum of consecutive naturals, for example, 3886670871 + ... + 3886676313.

It is an arithmetic number, because the mean of its divisors is an integer number (224748326700).

Almost surely, 2^{21155164361256} 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 21155164361256, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28767785817600).

21155164361256 is an abundant number, since it is smaller than the sum of its proper divisors (36380407273944).

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

21155164361256 is a wasteful number, since it uses less digits than its factorization.

21155164361256 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7800 (or 7796 counting only the distinct ones).

The product of its digits is 1296000, while the sum is 48.

The spelling of 21155164361256 in words is "twenty-one trillion, one hundred fifty-five billion, one hundred sixty-four million, three hundred sixty-one thousand, two hundred fifty-six".