399566509 has 4 divisors (see below), whose sum is σ = 401876316. Its totient is φ = 397256704.

The previous prime is 399566507. The next prime is 399566513. The reversal of 399566509 is 905665993.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 240932484 + 158634025 = 15522^2 + 12595^2 .

It is a cyclic number.

It is not a de Polignac number, because 399566509 - 2¹ = 399566507 is a prime.

It is a super-2 number, since 2×399566509² = 319306790228894162, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (399566501) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1154644 + ... + 1154989.

It is an arithmetic number, because the mean of its divisors is an integer number (100469079).

Almost surely, 2^399566509 is an apocalyptic number.

It is an amenable number.

399566509 is a deficient number, since it is larger than the sum of its proper divisors (2309807).

399566509 is a wasteful number, since it uses less digits than its factorization.

399566509 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2309806.

The product of its (nonzero) digits is 1968300, while the sum is 52.

The square root of 399566509 is about 19989.1597872447. The cubic root of 399566509 is about 736.5400377700.

The spelling of 399566509 in words is "three hundred ninety-nine million, five hundred sixty-six thousand, five hundred nine".