399640 has 32 divisors (see below), whose sum is σ = 917280. Its totient is φ = 156672.

The previous prime is 399617. The next prime is 399643. The reversal of 399640 is 46993.

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (399643) by changing a digit.

399640 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

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 7 ways as a sum of consecutive naturals, for example, 3829 + ... + 3931.

It is an arithmetic number, because the mean of its divisors is an integer number (28665).

2³⁹⁹⁶⁴⁰ is an apocalyptic number.

It is an amenable number.

399640 is an abundant number, since it is smaller than the sum of its proper divisors (517640).

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

399640 is a wasteful number, since it uses less digits than its factorization.

399640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 211 (or 207 counting only the distinct ones).

The product of its (nonzero) digits is 5832, while the sum is 31.

The square root of 399640 is about 632.1708629793. The cubic root of 399640 is about 73.6585191492.

The spelling of 399640 in words is "three hundred ninety-nine thousand, six hundred forty".