399381 has 16 divisors (see below), whose sum is σ = 580608. Its totient is φ = 243200.

The previous prime is 399379. The next prime is 399389. The reversal of 399381 is 183993.

It is a 5-Lehmer number, since φ(399381) divides (399381-1)⁵.

It is a cyclic number.

It is not a de Polignac number, because 399381 - 2¹ = 399379 is a prime.

It is a super-2 number, since 2×399381² = 319010366322, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (399389) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1996 + ... + 2186.

It is an arithmetic number, because the mean of its divisors is an integer number (36288).

2³⁹⁹³⁸¹ is an apocalyptic number.

It is an amenable number.

399381 is a deficient number, since it is larger than the sum of its proper divisors (181227).

399381 is a wasteful number, since it uses less digits than its factorization.

399381 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 252.

The product of its digits is 5832, while the sum is 33.

The square root of 399381 is about 631.9659800970. The cubic root of 399381 is about 73.6426034257.

It can be divided in two parts, 399 and 381, that added together give a triangular number (780 = T₃₉).

The spelling of 399381 in words is "three hundred ninety-nine thousand, three hundred eighty-one".