644444020 has 96 divisors (see below), whose sum is σ = 1516838400. Its totient is φ = 228009600.

The previous prime is 644444011. The next prime is 644444039. The reversal of 644444020 is 20444446.

It is a self number, because there is not a number n which added to its sum of digits gives 644444020.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 1700191 + ... + 1700569.

It is an arithmetic number, because the mean of its divisors is an integer number (15800400).

Almost surely, 2^644444020 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 644444020, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (758419200).

644444020 is an abundant number, since it is smaller than the sum of its proper divisors (872394380).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

644444020 is a wasteful number, since it uses less digits than its factorization.

644444020 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 589 (or 587 counting only the distinct ones).

The product of its (nonzero) digits is 12288, while the sum is 28.

The square root of 644444020 is about 25385.9019930354. The cubic root of 644444020 is about 863.7639333489.

Adding to 644444020 its reverse (20444446), we get a palindrome (664888466).

The spelling of 644444020 in words is "six hundred forty-four million, four hundred forty-four thousand, twenty".