399966 has 32 divisors (see below), whose sum is σ = 933120. Its totient is φ = 111936.

The previous prime is 399953. The next prime is 399979. The reversal of 399966 is 669993.

It is an interprime number because it is at equal distance from previous prime (399953) and next prime (399979).

It is a Harshad number since it is a multiple of its sum of digits (42).

It is a zygodrome in base 13.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 3685 + ... + 3791.

It is an arithmetic number, because the mean of its divisors is an integer number (29160).

2³⁹⁹⁹⁶⁶ is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 399966, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (466560).

399966 is an abundant number, since it is smaller than the sum of its proper divisors (533154).

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

399966 is a wasteful number, since it uses less digits than its factorization.

399966 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 208.

The product of its digits is 78732, while the sum is 42.

The square root of 399966 is about 632.4286521024. The cubic root of 399966 is about 73.6785422958.

The spelling of 399966 in words is "three hundred ninety-nine thousand, nine hundred sixty-six".