644422221 has 12 divisors (see below), whose sum is σ = 979823520. Its totient is φ = 407003400.

The previous prime is 644422201. The next prime is 644422223. The reversal of 644422221 is 122224446.

It is not a de Polignac number, because 644422221 - 2¹⁴ = 644405837 is a prime.

It is a nialpdrome in base 10.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644422223) 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, 1884105 + ... + 1884446.

It is an arithmetic number, because the mean of its divisors is an integer number (81651960).

Almost surely, 2^644422221 is an apocalyptic number.

It is an amenable number.

644422221 is a deficient number, since it is larger than the sum of its proper divisors (335401299).

644422221 is a wasteful number, since it uses less digits than its factorization.

644422221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3768576 (or 3768573 counting only the distinct ones).

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

The square root of 644422221 is about 25385.4726369237. The cubic root of 644422221 is about 863.7541939964.

Adding to 644422221 its reverse (122224446), we get a palindrome (766646667).

The spelling of 644422221 in words is "six hundred forty-four million, four hundred twenty-two thousand, two hundred twenty-one".