639389 has 4 divisors (see below), whose sum is σ = 641724. Its totient is φ = 637056.

The previous prime is 639371. The next prime is 639391. The reversal of 639389 is 983936.

It is a happy number.

639389 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.

It can be written as a sum of positive squares in 2 ways, for example, as 267289 + 372100 = 517^2 + 610^2 .

It is a cyclic number.

It is not a de Polignac number, because 639389 - 2¹² = 635293 is a prime.

It is an Ulam number.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (639329) 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, 692 + ... + 1325.

It is an arithmetic number, because the mean of its divisors is an integer number (160431).

2⁶³⁹³⁸⁹ is an apocalyptic number.

It is an amenable number.

639389 is a deficient number, since it is larger than the sum of its proper divisors (2335).

639389 is a wasteful number, since it uses less digits than its factorization.

639389 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2334.

The product of its digits is 34992, while the sum is 38.

The square root of 639389 is about 799.6180338136. The cubic root of 639389 is about 86.1499547112.

The spelling of 639389 in words is "six hundred thirty-nine thousand, three hundred eighty-nine".