391663 has 4 divisors (see below), whose sum is σ = 414720. Its totient is φ = 368608.

The previous prime is 391661. The next prime is 391679. The reversal of 391663 is 366193.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 391663 - 2¹ = 391661 is a prime.

It is a Duffinian number.

391663 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (391661) 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, 11503 + ... + 11536.

It is an arithmetic number, because the mean of its divisors is an integer number (103680).

2³⁹¹⁶⁶³ is an apocalyptic number.

391663 is a deficient number, since it is larger than the sum of its proper divisors (23057).

391663 is a wasteful number, since it uses less digits than its factorization.

391663 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 23056.

The product of its digits is 2916, while the sum is 28.

The square root of 391663 is about 625.8298490804. The cubic root of 391663 is about 73.1651356362.

The spelling of 391663 in words is "three hundred ninety-one thousand, six hundred sixty-three".