21561730848 has 360 divisors, whose sum is σ = 73807227648. Its totient is φ = 6048857088.

The previous prime is 21561730837. The next prime is 21561730849. The reversal of 21561730848 is 84803716512.

21561730848 is a `hidden beast` number, since 2 + 1 + 561 + 7 + 3 + 0 + 84 + 8 = 666.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21561730849) by changing a digit.

It is a polite number, since it can be written in 59 ways as a sum of consecutive naturals, for example, 96689265 + ... + 96689487.

Almost surely, 2^21561730848 is an apocalyptic number.

21561730848 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 21561730848, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (36903613824).

21561730848 is an abundant number, since it is smaller than the sum of its proper divisors (52245496800).

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

21561730848 is an equidigital number, since it uses as much as digits as its factorization.

21561730848 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 398 (or 308 counting only the distinct ones).

The product of its (nonzero) digits is 322560, while the sum is 45.

The spelling of 21561730848 in words is "twenty-one billion, five hundred sixty-one million, seven hundred thirty thousand, eight hundred forty-eight".