21243324521 has 4 divisors (see below), whose sum is σ = 21258006912. Its totient is φ = 21228642132.

The previous prime is 21243324503. The next prime is 21243324551. The reversal of 21243324521 is 12542334212.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21243324521 - 2³⁴ = 4063455337 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21243324551) by changing a digit.

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 3 ways as a sum of consecutive naturals, for example, 7339025 + ... + 7341918.

It is an arithmetic number, because the mean of its divisors is an integer number (5314501728).

Almost surely, 2^21243324521 is an apocalyptic number.

It is an amenable number.

21243324521 is a deficient number, since it is larger than the sum of its proper divisors (14682391).

21243324521 is a wasteful number, since it uses less digits than its factorization.

21243324521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 14682390.

The product of its digits is 11520, while the sum is 29.

Adding to 21243324521 its reverse (12542334212), we get a palindrome (33785658733).

The spelling of 21243324521 in words is "twenty-one billion, two hundred forty-three million, three hundred twenty-four thousand, five hundred twenty-one".