644221441 has 4 divisors (see below), whose sum is σ = 645613312. Its totient is φ = 642829572.

The previous prime is 644221439. The next prime is 644221453. The reversal of 644221441 is 144122446.

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 644221441 - 2¹ = 644221439 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (644221741) 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, 695241 + ... + 696166.

It is an arithmetic number, because the mean of its divisors is an integer number (161403328).

Almost surely, 2^644221441 is an apocalyptic number.

It is an amenable number.

644221441 is a deficient number, since it is larger than the sum of its proper divisors (1391871).

644221441 is a wasteful number, since it uses less digits than its factorization.

644221441 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1391870.

The product of its digits is 6144, while the sum is 28.

The square root of 644221441 is about 25381.5177048182. The cubic root of 644221441 is about 863.6644792227.

Adding to 644221441 its reverse (144122446), we get a palindrome (788343887).

It can be divided in two parts, 6442214 and 41, that added together give a triangular number (6442255 = T₃₅₈₉).

The spelling of 644221441 in words is "six hundred forty-four million, two hundred twenty-one thousand, four hundred forty-one".