399961 has 4 divisors (see below), whose sum is σ = 406800. Its totient is φ = 393124.

The previous prime is 399953. The next prime is 399979. The reversal of 399961 is 169993.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 399961 - 2³ = 399953 is a prime.

It is an Ulam number.

It is a Duffinian number.

399961 is a lucky number.

It is a self number, because there is not a number n which added to its sum of digits gives 399961.

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 3 ways as a sum of consecutive naturals, for example, 3331 + ... + 3448.

It is an arithmetic number, because the mean of its divisors is an integer number (101700).

2³⁹⁹⁹⁶¹ is an apocalyptic number.

It is an amenable number.

399961 is a deficient number, since it is larger than the sum of its proper divisors (6839).

399961 is an equidigital number, since it uses as much as digits as its factorization.

399961 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6838.

The product of its digits is 13122, while the sum is 37.

The square root of 399961 is about 632.4246990749. The cubic root of 399961 is about 73.6782352745.

It can be divided in two parts, 39 and 9961, that added together give a 4-th power (10000 = 10⁴).

The spelling of 399961 in words is "three hundred ninety-nine thousand, nine hundred sixty-one".