391666 has 16 divisors (see below), whose sum is σ = 675360. Its totient is φ = 168480.

The previous prime is 391661. The next prime is 391679. The reversal of 391666 is 666193.

391666 is digitally balanced in base 3, because in such base it contains all the possibile digits an equal number of times.

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

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, 51 + ... + 886.

It is an arithmetic number, because the mean of its divisors is an integer number (42210).

2³⁹¹⁶⁶⁶ is an apocalyptic number.

391666 is a deficient number, since it is larger than the sum of its proper divisors (283694).

391666 is a wasteful number, since it uses less digits than its factorization.

391666 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 969.

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

The square root of 391666 is about 625.8322458934. The cubic root of 391666 is about 73.1653224420.

The spelling of 391666 in words is "three hundred ninety-one thousand, six hundred sixty-six".