644224221 has 12 divisors (see below), whose sum is σ = 931275072. Its totient is φ = 429146376.

The previous prime is 644224211. The next prime is 644224247. The reversal of 644224221 is 122422446.

644224221 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is not a de Polignac number, because 644224221 - 2²¹ = 642127069 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644224211) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 15621 + ... + 39146.

It is an arithmetic number, because the mean of its divisors is an integer number (77606256).

Almost surely, 2^644224221 is an apocalyptic number.

It is an amenable number.

644224221 is a deficient number, since it is larger than the sum of its proper divisors (287050851).

644224221 is a wasteful number, since it uses less digits than its factorization.

644224221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 56080 (or 56077 counting only the distinct ones).

The product of its digits is 6144, while the sum is 27.

The square root of 644224221 is about 25381.5724690178. The cubic root of 644224221 is about 863.6657215408.

Adding to 644224221 its reverse (122422446), we get a palindrome (766646667).

The spelling of 644224221 in words is "six hundred forty-four million, two hundred twenty-four thousand, two hundred twenty-one".