665321 has 4 divisors (see below), whose sum is σ = 694272. Its totient is φ = 636372.

The previous prime is 665311. The next prime is 665351. The reversal of 665321 is 123566.

665321 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 665321 - 2¹⁴ = 648937 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (23), and also a Moran number because the ratio is a prime number: 28927 = 665321 / (6 + 6 + 5 + 3 + 2 + 1).

It is a Duffinian number.

It is a plaindrome in base 14.

It is a nialpdrome in base 10.

It is not an unprimeable number, because it can be changed into a prime (665311) 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, 14441 + ... + 14486.

It is an arithmetic number, because the mean of its divisors is an integer number (173568).

2⁶⁶⁵³²¹ is an apocalyptic number.

It is an amenable number.

665321 is a deficient number, since it is larger than the sum of its proper divisors (28951).

665321 is a wasteful number, since it uses less digits than its factorization.

665321 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 28950.

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

The square root of 665321 is about 815.6721154974. The cubic root of 665321 is about 87.2992294762.

Adding to 665321 its reverse (123566), we get a palindrome (788887).

The spelling of 665321 in words is "six hundred sixty-five thousand, three hundred twenty-one".