21288856056 has 128 divisors (see below), whose sum is σ = 59066810880. Its totient is φ = 6351561216.

The previous prime is 21288856049. The next prime is 21288856081. The reversal of 21288856056 is 65065888212.

It is a congruent number.

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 31 ways as a sum of consecutive naturals, for example, 3541005 + ... + 3547011.

It is an arithmetic number, because the mean of its divisors is an integer number (461459460).

Almost surely, 2^21288856056 is an apocalyptic number.

21288856056 is a gapful number since it is divisible by the number (26) 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 21288856056, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29533405440).

21288856056 is an abundant number, since it is smaller than the sum of its proper divisors (37777954824).

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

21288856056 is a wasteful number, since it uses less digits than its factorization.

21288856056 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6373 (or 6369 counting only the distinct ones).

The product of its (nonzero) digits is 1843200, while the sum is 51.

The spelling of 21288856056 in words is "twenty-one billion, two hundred eighty-eight million, eight hundred fifty-six thousand, fifty-six".