391668 has 24 divisors (see below), whose sum is σ = 924672. Its totient is φ = 129024.

The previous prime is 391661. The next prime is 391679. The reversal of 391668 is 866193.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (391661) by changing a digit.

391668 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 (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1396 + ... + 1652.

It is an arithmetic number, because the mean of its divisors is an integer number (38528).

2³⁹¹⁶⁶⁸ is an apocalyptic number.

It is an amenable number.

391668 is an abundant number, since it is smaller than the sum of its proper divisors (533004).

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

391668 is a wasteful number, since it uses less digits than its factorization.

391668 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 391 (or 389 counting only the distinct ones).

The product of its digits is 7776, while the sum is 33.

The square root of 391668 is about 625.8338437637. The cubic root of 391668 is about 73.1654469788.

The spelling of 391668 in words is "three hundred ninety-one thousand, six hundred sixty-eight".