399866 has 4 divisors (see below), whose sum is σ = 599802. Its totient is φ = 199932.

The previous prime is 399853. The next prime is 399871. The reversal of 399866 is 668993.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 668993 = 13 ⋅51461.

It can be written as a sum of positive squares in only one way, i.e., 395641 + 4225 = 629^2 + 65^2 .

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 99965 + ... + 99968.

2³⁹⁹⁸⁶⁶ is an apocalyptic number.

399866 is a deficient number, since it is larger than the sum of its proper divisors (199936).

399866 is a wasteful number, since it uses less digits than its factorization.

399866 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 199935.

The product of its digits is 69984, while the sum is 41.

The square root of 399866 is about 632.3495868584. The cubic root of 399866 is about 73.6724013835.

The spelling of 399866 in words is "three hundred ninety-nine thousand, eight hundred sixty-six".