21229537568 has 54 divisors (see below), whose sum is σ = 42861803859. Its totient is φ = 10350604992.

The previous prime is 21229537561. The next prime is 21229537573. The reversal of 21229537568 is 86573592212.

It is a happy number.

It is a powerful number, because all its prime factors have an exponent greater than 1 and also an Achilles number because it is not a perfect power.

It can be written as a sum of positive squares in only one way, i.e., 10614768784 + 10614768784 = 103028^2 + 103028^2 .

It is an ABA number since it can be written as A⋅B^A, here for A=2, B=103028.

It is a super-2 number, since 2×21229537568² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21229537561) by changing a digit.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 35441333 + ... + 35441931.

Almost surely, 2^21229537568 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 21229537568

21229537568 is an abundant number, since it is smaller than the sum of its proper divisors (21632266291).

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

21229537568 is an frugal number, since it uses more digits than its factorization.

21229537568 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1294 (or 644 counting only the distinct ones).

The product of its digits is 1814400, while the sum is 50.

Multiplying 21229537568 by its sum of digits (50), we get a square (1061476878400 = 1030280²).

The spelling of 21229537568 in words is "twenty-one billion, two hundred twenty-nine million, five hundred thirty-seven thousand, five hundred sixty-eight".