21001885856 has 96 divisors (see below), whose sum is σ = 49665208320. Its totient is φ = 8547238656.

The previous prime is 21001885843. The next prime is 21001885873. The reversal of 21001885856 is 65858810012.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 701465 + ... + 730791.

It is an arithmetic number, because the mean of its divisors is an integer number (517345920).

Almost surely, 2^21001885856 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 21001885856, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24832604160).

21001885856 is an abundant number, since it is smaller than the sum of its proper divisors (28663322464).

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

21001885856 is a wasteful number, since it uses less digits than its factorization.

21001885856 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 29506 (or 29498 counting only the distinct ones).

The product of its (nonzero) digits is 153600, while the sum is 44.

The spelling of 21001885856 in words is "twenty-one billion, one million, eight hundred eighty-five thousand, eight hundred fifty-six".