644804 has 6 divisors (see below), whose sum is σ = 1128414. Its totient is φ = 322400.

The previous prime is 644801. The next prime is 644837. The reversal of 644804 is 408446.

644804 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in only one way, i.e., 643204 + 1600 = 802^2 + 40^2 .

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 644804.

It is not an unprimeable number, because it can be changed into a prime (644801) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 80597 + ... + 80604.

It is an arithmetic number, because the mean of its divisors is an integer number (188069).

2⁶⁴⁴⁸⁰⁴ is an apocalyptic number.

It is an amenable number.

644804 is a deficient number, since it is larger than the sum of its proper divisors (483610).

644804 is a wasteful number, since it uses less digits than its factorization.

644804 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 161205 (or 161203 counting only the distinct ones).

The product of its (nonzero) digits is 3072, while the sum is 26.

The square root of 644804 is about 802.9968866689. The cubic root of 644804 is about 86.3924733384.

The spelling of 644804 in words is "six hundred forty-four thousand, eight hundred four".