21424443221 has 4 divisors (see below), whose sum is σ = 21441039744. Its totient is φ = 21407846700.

The previous prime is 21424443211. The next prime is 21424443247. The reversal of 21424443221 is 12234442412.

It is a happy number.

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 a de Polignac number, because none of the positive numbers 2^k-21424443221 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21424443211) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 8296325 + ... + 8298906.

It is an arithmetic number, because the mean of its divisors is an integer number (5360259936).

Almost surely, 2^21424443221 is an apocalyptic number.

It is an amenable number.

21424443221 is a deficient number, since it is larger than the sum of its proper divisors (16596523).

21424443221 is a wasteful number, since it uses less digits than its factorization.

21424443221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 16596522.

The product of its digits is 12288, while the sum is 29.

Adding to 21424443221 its reverse (12234442412), we get a palindrome (33658885633).

The spelling of 21424443221 in words is "twenty-one billion, four hundred twenty-four million, four hundred forty-three thousand, two hundred twenty-one".