321399665 has 4 divisors (see below), whose sum is σ = 385679604. Its totient is φ = 257119728.

The previous prime is 321399629. The next prime is 321399707. The reversal of 321399665 is 566993123.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 566993123 = 29 ⋅19551487.

It can be written as a sum of positive squares in 2 ways, for example, as 154654096 + 166745569 = 12436^2 + 12913^2 .

It is a cyclic number.

It is not a de Polignac number, because 321399665 - 2⁸ = 321399409 is a prime.

It is a super-2 number, since 2×321399665² = 206595489324224450, which contains 22 as substring.

It is a Duffinian number.

It is an unprimeable number.

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 3 ways as a sum of consecutive naturals, for example, 32139962 + ... + 32139971.

It is an arithmetic number, because the mean of its divisors is an integer number (96419901).

Almost surely, 2^321399665 is an apocalyptic number.

It is an amenable number.

321399665 is a deficient number, since it is larger than the sum of its proper divisors (64279939).

321399665 is an equidigital number, since it uses as much as digits as its factorization.

321399665 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 64279938.

The product of its digits is 262440, while the sum is 44.

The square root of 321399665 is about 17927.6229601138. The cubic root of 321399665 is about 684.9861755073.

The spelling of 321399665 in words is "three hundred twenty-one million, three hundred ninety-nine thousand, six hundred sixty-five".