1664321 has 4 divisors (see below), whose sum is σ = 1679700. Its totient is φ = 1648944.

The previous prime is 1664291. The next prime is 1664353. The reversal of 1664321 is 1234661.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 1234661 = 103 ⋅11987.

It can be written as a sum of positive squares in 2 ways, for example, as 960400 + 703921 = 980^2 + 839^2 .

It is a cyclic number.

It is not a de Polignac number, because 1664321 - 2¹⁴ = 1647937 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1664021) 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, 7526 + ... + 7743.

It is an arithmetic number, because the mean of its divisors is an integer number (419925).

2^1664321 is an apocalyptic number.

It is an amenable number.

1664321 is a deficient number, since it is larger than the sum of its proper divisors (15379).

1664321 is a wasteful number, since it uses less digits than its factorization.

1664321 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 15378.

The product of its digits is 864, while the sum is 23.

The square root of 1664321 is about 1290.0856560709. The cubic root of 1664321 is about 118.5074621281.

Adding to 1664321 its reverse (1234661), we get a palindrome (2898982).

The spelling of 1664321 in words is "one million, six hundred sixty-four thousand, three hundred twenty-one".