19664321 has 4 divisors (see below), whose sum is σ = 19681200. Its totient is φ = 19647444.

The previous prime is 19664273. The next prime is 19664341. The reversal of 19664321 is 12346691.

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, and also an emirpimes, since its reverse is a distinct semiprime: 12346691 = 7 ⋅1763813.

It is a cyclic number.

It is not a de Polignac number, because 19664321 - 2¹⁸ = 19402177 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (19664341) 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, 6551 + ... + 9068.

It is an arithmetic number, because the mean of its divisors is an integer number (4920300).

Almost surely, 2^19664321 is an apocalyptic number.

It is an amenable number.

19664321 is a deficient number, since it is larger than the sum of its proper divisors (16879).

19664321 is a wasteful number, since it uses less digits than its factorization.

19664321 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16878.

The product of its digits is 7776, while the sum is 32.

The square root of 19664321 is about 4434.4470906755. The cubic root of 19664321 is about 269.9145637318.

The spelling of 19664321 in words is "nineteen million, six hundred sixty-four thousand, three hundred twenty-one".