644766444 has 144 divisors (see below), whose sum is σ = 1971540480. Its totient is φ = 173560320.

The previous prime is 644766443. The next prime is 644766449. The reversal of 644766444 is 444667446.

It is a nude number because it is divisible by every one of its digits.

It is a self number, because there is not a number n which added to its sum of digits gives 644766444.

It is not an unprimeable number, because it can be changed into a prime (644766443) by changing a digit.

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 47 ways as a sum of consecutive naturals, for example, 1488852 + ... + 1489284.

Almost surely, 2^644766444 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 644766444, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (985770240).

644766444 is an abundant number, since it is smaller than the sum of its proper divisors (1326774036).

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

644766444 is a wasteful number, since it uses less digits than its factorization.

644766444 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 780 (or 775 counting only the distinct ones).

The product of its digits is 1548288, while the sum is 45.

The square root of 644766444 is about 25392.2516528172. The cubic root of 644766444 is about 863.9079602316.

The spelling of 644766444 in words is "six hundred forty-four million, seven hundred sixty-six thousand, four hundred forty-four".