6439 has 4 divisors (see below), whose sum is σ = 6624. Its totient is φ = 6256.

The previous prime is 6427. The next prime is 6449. The reversal of 6439 is 9346.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 9346 = 2 ⋅4673.

It is a cyclic number.

It is not a de Polignac number, because 6439 - 2⁷ = 6311 is a prime.

It is a Smith number, since the sum of its digits (22) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a plaindrome in base 8 and base 14.

It is a nialpdrome in base 3 and base 9.

It is a zygodrome in base 3.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (6449) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 22 + ... + 115.

It is an arithmetic number, because the mean of its divisors is an integer number (1656).

2⁶⁴³⁹ is an apocalyptic number.

6439 is a deficient number, since it is larger than the sum of its proper divisors (185).

6439 is a wasteful number, since it uses less digits than its factorization.

6439 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 184.

The product of its digits is 648, while the sum is 22.

The square root of 6439 is about 80.2433797892. The cubic root of 6439 is about 18.6039918977.

The spelling of 6439 in words is "six thousand, four hundred thirty-nine".