644704 has 12 divisors (see below), whose sum is σ = 1269324. Its totient is φ = 322336.

The previous prime is 644701. The next prime is 644717. The reversal of 644704 is 407446.

It is a happy number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644701) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10042 + ... + 10105.

It is an arithmetic number, because the mean of its divisors is an integer number (105777).

2⁶⁴⁴⁷⁰⁴ is an apocalyptic number.

It is an amenable number.

644704 is a deficient number, since it is larger than the sum of its proper divisors (624620).

644704 is a wasteful number, since it uses less digits than its factorization.

644704 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 20157 (or 20149 counting only the distinct ones).

The product of its (nonzero) digits is 2688, while the sum is 25.

The square root of 644704 is about 802.9346175125. The cubic root of 644704 is about 86.3880070231.

The spelling of 644704 in words is "six hundred forty-four thousand, seven hundred four".