6439999 has 4 divisors (see below), whose sum is σ = 6482800. Its totient is φ = 6397200.

The previous prime is 6439997. The next prime is 6440003. The reversal of 6439999 is 9999346.

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 6439999 - 2¹ = 6439997 is a prime.

It is a Duffinian number.

6439999 is a modest number, since divided by 9999 gives 643 as remainder.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (6439997) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 21174 + ... + 21475.

It is an arithmetic number, because the mean of its divisors is an integer number (1620700).

Almost surely, 2^6439999 is an apocalyptic number.

6439999 is a deficient number, since it is larger than the sum of its proper divisors (42801).

6439999 is a wasteful number, since it uses less digits than its factorization.

6439999 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 42800.

The product of its digits is 472392, while the sum is 49.

The square root of 6439999 is about 2537.7153110623. The cubic root of 6439999 is about 186.0495397391.

The spelling of 6439999 in words is "six million, four hundred thirty-nine thousand, nine hundred ninety-nine".