644399 has 6 divisors (see below), whose sum is σ = 749664. Its totient is φ = 552300.

The previous prime is 644383. The next prime is 644401. The reversal of 644399 is 993446.

It is a happy number.

It is not a de Polignac number, because 644399 - 2⁴ = 644383 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 (644359) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 6527 + ... + 6624.

It is an arithmetic number, because the mean of its divisors is an integer number (124944).

2⁶⁴⁴³⁹⁹ is an apocalyptic number.

644399 is a deficient number, since it is larger than the sum of its proper divisors (105265).

644399 is a wasteful number, since it uses less digits than its factorization.

644399 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 13165 (or 13158 counting only the distinct ones).

The product of its digits is 23328, while the sum is 35.

The square root of 644399 is about 802.7446667528. The cubic root of 644399 is about 86.3743819082.

The spelling of 644399 in words is "six hundred forty-four thousand, three hundred ninety-nine".