21597531648 has 480 divisors, whose sum is σ = 76914541440. Its totient is φ = 5310627840.

The previous prime is 21597531623. The next prime is 21597531649. The reversal of 21597531648 is 84613579512.

It is a self number, because there is not a number n which added to its sum of digits gives 21597531648.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21597531649) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 15729490 + ... + 15730862.

It is an arithmetic number, because the mean of its divisors is an integer number (160238628).

Almost surely, 2^21597531648 is an apocalyptic number.

21597531648 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 21597531648, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (38457270720).

21597531648 is an abundant number, since it is smaller than the sum of its proper divisors (55317009792).

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

21597531648 is a wasteful number, since it uses less digits than its factorization.

21597531648 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1438 (or 1415 counting only the distinct ones).

The product of its digits is 1814400, while the sum is 51.

The spelling of 21597531648 in words is "twenty-one billion, five hundred ninety-seven million, five hundred thirty-one thousand, six hundred forty-eight".