6399520009 has 3 divisors (see below), whose sum is σ = 6399600007. Its totient is φ = 6399440012.

The previous prime is 6399520003. The next prime is 6399520013. The reversal of 6399520009 is 9000259936.

The square root of 6399520009 is 79997.

It is a perfect power (a square), and thus also a powerful number.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in only one way, i.e., 619263225 + 5780256784 = 24885^2 + 76028^2 .

It is not a de Polignac number, because 6399520009 - 2⁷ = 6399519881 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (6399520003) by changing a digit.

It is a polite number, since it can be written in 2 ways as a sum of consecutive naturals, for example, 39999 + ... + 119995.

Almost surely, 2^6399520009 is an apocalyptic number.

6399520009 is the 79997-th square number.

6399520009 is the 39999-th centered octagonal number.

It is an amenable number.

6399520009 is a deficient number, since it is larger than the sum of its proper divisors (79998).

6399520009 is an frugal number, since it uses more digits than its factorization.

6399520009 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 159994 (or 79997 counting only the distinct ones).

The product of its (nonzero) digits is 131220, while the sum is 43.

The cubic root of 6399520009 is about 1856.5891172667.

The spelling of 6399520009 in words is "six billion, three hundred ninety-nine million, five hundred twenty thousand, nine".