399691509 has 16 divisors (see below), whose sum is σ = 614447232. Its totient is φ = 226372608.

The previous prime is 399691483. The next prime is 399691529. The reversal of 399691509 is 905196993.

It is not a de Polignac number, because 399691509 - 2⁹ = 399690997 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (399691529) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 81844 + ... + 86589.

It is an arithmetic number, because the mean of its divisors is an integer number (38402952).

Almost surely, 2^399691509 is an apocalyptic number.

It is an amenable number.

399691509 is a deficient number, since it is larger than the sum of its proper divisors (214755723).

399691509 is a wasteful number, since it uses less digits than its factorization.

399691509 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 168556.

The product of its (nonzero) digits is 590490, while the sum is 51.

The square root of 399691509 is about 19992.2862374467. The cubic root of 399691509 is about 736.6168359197.

The spelling of 399691509 in words is "three hundred ninety-nine million, six hundred ninety-one thousand, five hundred nine".