321665 has 4 divisors (see below), whose sum is σ = 386004. Its totient is φ = 257328.

The previous prime is 321661. The next prime is 321679. The reversal of 321665 is 566123.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 566123 = 491 ⋅1153.

It can be written as a sum of positive squares in 2 ways, for example, as 238144 + 83521 = 488^2 + 289^2 .

It is a cyclic number.

It is not a de Polignac number, because 321665 - 2² = 321661 is a prime.

It is a Duffinian number.

It is a nialpdrome in base 14.

It is a self number, because there is not a number n which added to its sum of digits gives 321665.

It is not an unprimeable number, because it can be changed into a prime (321661) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 32162 + ... + 32171.

It is an arithmetic number, because the mean of its divisors is an integer number (96501).

2³²¹⁶⁶⁵ is an apocalyptic number.

It is an amenable number.

321665 is a deficient number, since it is larger than the sum of its proper divisors (64339).

321665 is an equidigital number, since it uses as much as digits as its factorization.

321665 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 64338.

The product of its digits is 1080, while the sum is 23.

The square root of 321665 is about 567.1551815861. The cubic root of 321665 is about 68.5174622929.

Adding to 321665 its reverse (566123), we get a palindrome (887788).

The spelling of 321665 in words is "three hundred twenty-one thousand, six hundred sixty-five".