399509 has 4 divisors (see below), whose sum is σ = 435840. Its totient is φ = 363180.

The previous prime is 399499. The next prime is 399523. The reversal of 399509 is 905993.

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 a cyclic number.

It is not a de Polignac number, because 399509 - 2⁴ = 399493 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (399409) 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, 18149 + ... + 18170.

It is an arithmetic number, because the mean of its divisors is an integer number (108960).

2³⁹⁹⁵⁰⁹ is an apocalyptic number.

It is an amenable number.

399509 is a deficient number, since it is larger than the sum of its proper divisors (36331).

399509 is a wasteful number, since it uses less digits than its factorization.

399509 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 36330.

The product of its (nonzero) digits is 10935, while the sum is 35.

The square root of 399509 is about 632.0672432582. The cubic root of 399509 is about 73.6504699712.

The spelling of 399509 in words is "three hundred ninety-nine thousand, five hundred nine".