399921 has 8 divisors (see below), whose sum is σ = 538560. Its totient is φ = 263952.

The previous prime is 399913. The next prime is 399937. The reversal of 399921 is 129993.

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

It is not a de Polignac number, because 399921 - 2³ = 399913 is a prime.

It is not an unprimeable number, because it can be changed into a prime (399911) 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, 285 + ... + 938.

It is an arithmetic number, because the mean of its divisors is an integer number (67320).

2³⁹⁹⁹²¹ is an apocalyptic number.

It is an amenable number.

399921 is a deficient number, since it is larger than the sum of its proper divisors (138639).

399921 is a wasteful number, since it uses less digits than its factorization.

399921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1335.

The product of its digits is 4374, while the sum is 33.

The square root of 399921 is about 632.3930739659. The cubic root of 399921 is about 73.6757790120.

It can be divided in two parts, 39992 and 1, that added together give a palindrome (39993).

The spelling of 399921 in words is "three hundred ninety-nine thousand, nine hundred twenty-one".