391665 has 8 divisors (see below), whose sum is σ = 626688. Its totient is φ = 208880.

The previous prime is 391661. The next prime is 391679. The reversal of 391665 is 566193.

It is a happy number.

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

It is not a de Polignac number, because 391665 - 2² = 391661 is a prime.

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, 13041 + ... + 13070.

It is an arithmetic number, because the mean of its divisors is an integer number (78336).

2³⁹¹⁶⁶⁵ is an apocalyptic number.

It is an amenable number.

391665 is a deficient number, since it is larger than the sum of its proper divisors (235023).

391665 is a wasteful number, since it uses less digits than its factorization.

391665 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 26119.

The product of its digits is 4860, while the sum is 30.

The square root of 391665 is about 625.8314469568. The cubic root of 391665 is about 73.1652601735.

The spelling of 391665 in words is "three hundred ninety-one thousand, six hundred sixty-five".