399909 has 4 divisors (see below), whose sum is σ = 533216. Its totient is φ = 266604.

The previous prime is 399899. The next prime is 399911. The reversal of 399909 is 909993.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 399909 - 2⁷ = 399781 is a prime.

It is a D-number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (399979) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 66649 + ... + 66654.

It is an arithmetic number, because the mean of its divisors is an integer number (133304).

2³⁹⁹⁹⁰⁹ is an apocalyptic number.

It is an amenable number.

399909 is a deficient number, since it is larger than the sum of its proper divisors (133307).

399909 is a wasteful number, since it uses less digits than its factorization.

399909 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 133306.

The product of its (nonzero) digits is 19683, while the sum is 39.

The square root of 399909 is about 632.3835861248. The cubic root of 399909 is about 73.6750421013.

The spelling of 399909 in words is "three hundred ninety-nine thousand, nine hundred nine".