399984 has 40 divisors (see below), whose sum is σ = 1114512. Its totient is φ = 122880.

The previous prime is 399983. The next prime is 399989. The reversal of 399984 is 489993.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (399983) 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, 304 + ... + 944.

2³⁹⁹⁹⁸⁴ is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 399984, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (557256).

399984 is an abundant number, since it is smaller than the sum of its proper divisors (714528).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

399984 is a wasteful number, since it uses less digits than its factorization.

399984 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 665 (or 659 counting only the distinct ones).

The product of its digits is 69984, while the sum is 42.

The square root of 399984 is about 632.4428827965. The cubic root of 399984 is about 73.6796475513.

Subtracting 399984 from its reverse (489993), we obtain a palindrome (90009).

It can be divided in two parts, 39 and 9984, that multiplied together give a square (389376 = 624²).

The spelling of 399984 in words is "three hundred ninety-nine thousand, nine hundred eighty-four".