644389 has 4 divisors (see below), whose sum is σ = 649440. Its totient is φ = 639340.

The previous prime is 644383. The next prime is 644401. The reversal of 644389 is 983446.

644389 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 644389 - 2³ = 644381 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644381) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2329 + ... + 2590.

It is an arithmetic number, because the mean of its divisors is an integer number (162360).

2⁶⁴⁴³⁸⁹ is an apocalyptic number.

It is an amenable number.

644389 is a deficient number, since it is larger than the sum of its proper divisors (5051).

644389 is a wasteful number, since it uses less digits than its factorization.

644389 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5050.

The product of its digits is 20736, while the sum is 34.

The square root of 644389 is about 802.7384380980. The cubic root of 644389 is about 86.3739351103.

The spelling of 644389 in words is "six hundred forty-four thousand, three hundred eighty-nine".