320991 has 16 divisors (see below), whose sum is σ = 476928. Its totient is φ = 190400.

The previous prime is 320953. The next prime is 321007. The reversal of 320991 is 199023.

It is a happy number.

It is a cyclic number.

It is not a de Polignac number, because 320991 - 2⁶ = 320927 is a prime.

It is a Smith number, since the sum of its digits (24) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (320911) 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 15 ways as a sum of consecutive naturals, for example, 2275 + ... + 2411.

It is an arithmetic number, because the mean of its divisors is an integer number (29808).

2³²⁰⁹⁹¹ is an apocalyptic number.

320991 is a deficient number, since it is larger than the sum of its proper divisors (155937).

320991 is a wasteful number, since it uses less digits than its factorization.

320991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 222.

The product of its (nonzero) digits is 486, while the sum is 24.

The square root of 320991 is about 566.5606763622. The cubic root of 320991 is about 68.4695728612.

The spelling of 320991 in words is "three hundred twenty thousand, nine hundred ninety-one".