399991665 has 8 divisors (see below), whose sum is σ = 639986688. Its totient is φ = 213328880.

The previous prime is 399991663. The next prime is 399991727. The reversal of 399991665 is 566199993.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 399991665 - 2¹ = 399991663 is a prime.

It is not an unprimeable number, because it can be changed into a prime (399991663) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 13333041 + ... + 13333070.

It is an arithmetic number, because the mean of its divisors is an integer number (79998336).

Almost surely, 2^399991665 is an apocalyptic number.

It is an amenable number.

399991665 is a deficient number, since it is larger than the sum of its proper divisors (239995023).

399991665 is a wasteful number, since it uses less digits than its factorization.

399991665 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 26666119.

The product of its digits is 3542940, while the sum is 57.

The square root of 399991665 is about 19999.7916239145. The cubic root of 399991665 is about 736.8011819588.

The spelling of 399991665 in words is "three hundred ninety-nine million, nine hundred ninety-one thousand, six hundred sixty-five".