21206555328 has 224 divisors, whose sum is σ = 66946889728. Its totient is φ = 5797785600.

The previous prime is 21206555297. The next prime is 21206555339. The reversal of 21206555328 is 82355560212.

It is a tau number, because it is divible by the number of its divisors (224).

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 3029913 + ... + 3036903.

Almost surely, 2^21206555328 is an apocalyptic number.

21206555328 is a gapful number since it is divisible by the number (28) 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 21206555328, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33473444864).

21206555328 is an abundant number, since it is smaller than the sum of its proper divisors (45740334400).

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

21206555328 is a wasteful number, since it uses less digits than its factorization.

21206555328 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7111 (or 7101 counting only the distinct ones).

The product of its (nonzero) digits is 144000, while the sum is 39.

The spelling of 21206555328 in words is "twenty-one billion, two hundred six million, five hundred fifty-five thousand, three hundred twenty-eight".