644039 has 4 divisors (see below), whose sum is σ = 702600. Its totient is φ = 585480.

The previous prime is 644029. The next prime is 644047. The reversal of 644039 is 930446.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 644039 - 2¹⁶ = 578503 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 643999 and 644017.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644009) 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, 29264 + ... + 29285.

It is an arithmetic number, because the mean of its divisors is an integer number (175650).

2⁶⁴⁴⁰³⁹ is an apocalyptic number.

644039 is a deficient number, since it is larger than the sum of its proper divisors (58561).

644039 is a wasteful number, since it uses less digits than its factorization.

644039 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 58560.

The product of its (nonzero) digits is 2592, while the sum is 26.

The square root of 644039 is about 802.5204047250. The cubic root of 644039 is about 86.3582942721.

The spelling of 644039 in words is "six hundred forty-four thousand, thirty-nine".