399665989 has 8 divisors (see below), whose sum is σ = 404364312. Its totient is φ = 394982400.

The previous prime is 399665983. The next prime is 399665993. The reversal of 399665989 is 989566993.

It can be written as a sum of positive squares in 4 ways, for example, as 74476900 + 325189089 = 8630^2 + 18033^2 .

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

It is a cyclic number.

It is not a de Polignac number, because 399665989 - 2⁹ = 399665477 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 399665989.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (399665983) 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, 56557 + ... + 63229.

It is an arithmetic number, because the mean of its divisors is an integer number (50545539).

Almost surely, 2^399665989 is an apocalyptic number.

It is an amenable number.

399665989 is a deficient number, since it is larger than the sum of its proper divisors (4698323).

399665989 is a wasteful number, since it uses less digits than its factorization.

399665989 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7367.

The product of its digits is 28343520, while the sum is 64.

The square root of 399665989 is about 19991.6479810945. The cubic root of 399665989 is about 736.6011581104.

The spelling of 399665989 in words is "three hundred ninety-nine million, six hundred sixty-five thousand, nine hundred eighty-nine".