6399999999 has 16 divisors (see below), whose sum is σ = 9484800000. Its totient is φ = 4265173368.

The previous prime is 6399999959. The next prime is 6400000007. The reversal of 6399999999 is 9999999936.

It is a Cunningham number, because it is equal to 80000²-1.

It is not a de Polignac number, because 6399999999 - 2⁸ = 6399999743 is a prime.

6399999999 is a modest number, since divided by 99999 gives 63999 as remainder.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (6399999959) 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, 40002 + ... + 120000.

It is an arithmetic number, because the mean of its divisors is an integer number (592800000).

Almost surely, 2^6399999999 is an apocalyptic number.

6399999999 is a deficient number, since it is larger than the sum of its proper divisors (3084800001).

6399999999 is a wasteful number, since it uses less digits than its factorization.

6399999999 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 82971 (or 82965 counting only the distinct ones).

The product of its digits is 774840978, while the sum is 81.

The square root of 6399999999 is about 79999.9999937500. Note that the first 5 decimals coincide. The cubic root of 6399999999 is about 1856.6355333484.

The spelling of 6399999999 in words is "six billion, three hundred ninety-nine million, nine hundred ninety-nine thousand, nine hundred ninety-nine".