6399999 has 16 divisors (see below), whose sum is σ = 9525600. Its totient is φ = 4246848.

The previous prime is 6399971. The next prime is 6400013. The reversal of 6399999 is 9999936.

It is not a de Polignac number, because 6399999 - 2¹² = 6395903 is a prime.

6399999 is a modest number, since divided by 9999 gives 639 as remainder.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (6399929) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 7507 + ... + 8315.

It is an arithmetic number, because the mean of its divisors is an integer number (595350).

Almost surely, 2^6399999 is an apocalyptic number.

6399999 is a deficient number, since it is larger than the sum of its proper divisors (3125601).

6399999 is a wasteful number, since it uses less digits than its factorization.

6399999 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1111 (or 1105 counting only the distinct ones).

The product of its digits is 1062882, while the sum is 54.

The square root of 6399999 is about 2529.8219304923. The cubic root of 6399999 is about 185.6635436745.

The spelling of 6399999 in words is "six million, three hundred ninety-nine thousand, nine hundred ninety-nine".