21423444421 has 4 divisors (see below), whose sum is σ = 22683647052. Its totient is φ = 20163241792.

The previous prime is 21423444409. The next prime is 21423444437. The reversal of 21423444421 is 12444432412.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 14725822500 + 6697621921 = 121350^2 + 81839^2 .

It is a cyclic number.

It is not a de Polignac number, because 21423444421 - 2⁷ = 21423444293 is a prime.

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21423444401) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 630101290 + ... + 630101323.

It is an arithmetic number, because the mean of its divisors is an integer number (5670911763).

Almost surely, 2^21423444421 is an apocalyptic number.

It is an amenable number.

21423444421 is a deficient number, since it is larger than the sum of its proper divisors (1260202631).

21423444421 is a wasteful number, since it uses less digits than its factorization.

21423444421 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1260202630.

The product of its digits is 24576, while the sum is 31.

Adding to 21423444421 its reverse (12444432412), we get a palindrome (33867876833).

The spelling of 21423444421 in words is "twenty-one billion, four hundred twenty-three million, four hundred forty-four thousand, four hundred twenty-one".