21397229568 has 780 divisors, whose sum is σ = 77508844644. Its totient is φ = 5839257600.

The previous prime is 21397229549. The next prime is 21397229573. The reversal of 21397229568 is 86592279312.

21397229568 is a `hidden beast` number, since 2 + 1 + 3 + 9 + 72 + 2 + 9 + 568 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 1967099904 + 19430129664 = 44352^2 + 139392^2 .

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

Its product of digits (3265920) is a multiple of the sum of its prime divisors (70).

It is a congruent number.

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 59 ways as a sum of consecutive naturals, for example, 521883628 + ... + 521883668.

Almost surely, 2^21397229568 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 21397229568, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (38754422322).

21397229568 is an abundant number, since it is smaller than the sum of its proper divisors (56111615076).

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

21397229568 is a wasteful number, since it uses less digits than its factorization.

21397229568 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 112 (or 70 counting only the distinct ones).

The product of its digits is 3265920, while the sum is 54.

The spelling of 21397229568 in words is "twenty-one billion, three hundred ninety-seven million, two hundred twenty-nine thousand, five hundred sixty-eight".