21525569856 has 504 divisors, whose sum is σ = 76140844416. Its totient is φ = 6009292800.

The previous prime is 21525569803. The next prime is 21525569917. The reversal of 21525569856 is 65896552512.

It is a happy number.

21525569856 is a `hidden beast` number, since 2 + 1 + 5 + 2 + 556 + 9 + 85 + 6 = 666.

It is a tau number, because it is divible by the number of its divisors (504).

It is a Harshad number since it is a multiple of its sum of digits (54).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 71 ways as a sum of consecutive naturals, for example, 35815956 + ... + 35816556.

It is an arithmetic number, because the mean of its divisors is an integer number (151073104).

Almost surely, 2^21525569856 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 21525569856, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (38070422208).

21525569856 is an abundant number, since it is smaller than the sum of its proper divisors (54615274560).

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

21525569856 is an equidigital number, since it uses as much as digits as its factorization.

21525569856 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 689 (or 660 counting only the distinct ones).

The product of its digits is 6480000, while the sum is 54.

The spelling of 21525569856 in words is "twenty-one billion, five hundred twenty-five million, five hundred sixty-nine thousand, eight hundred fifty-six".