644635000 has 80 divisors (see below), whose sum is σ = 1519669800. Its totient is φ = 256272000.

The previous prime is 644634971. The next prime is 644635009. The reversal of 644635000 is 536446.

644635000 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a self number, because there is not a number n which added to its sum of digits gives 644635000.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644635009) by changing a digit.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 1144719 + ... + 1145281.

Almost surely, 2^644635000 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 644635000, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (759834900).

644635000 is an abundant number, since it is smaller than the sum of its proper divisors (875034800).

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

644635000 is a wasteful number, since it uses less digits than its factorization.

644635000 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 818 (or 799 counting only the distinct ones).

The product of its (nonzero) digits is 8640, while the sum is 28.

The square root of 644635000 is about 25389.6632510162. The cubic root of 644635000 is about 863.8492499619.

The spelling of 644635000 in words is "six hundred forty-four million, six hundred thirty-five thousand".