16668321 has 4 divisors (see below), whose sum is σ = 22224432. Its totient is φ = 11112212.

The previous prime is 16668319. The next prime is 16668329. The reversal of 16668321 is 12386661.

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 16668321 - 2¹ = 16668319 is a prime.

It is not an unprimeable number, because it can be changed into a prime (16668329) 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, 2778051 + ... + 2778056.

It is an arithmetic number, because the mean of its divisors is an integer number (5556108).

Almost surely, 2^16668321 is an apocalyptic number.

It is an amenable number.

16668321 is a deficient number, since it is larger than the sum of its proper divisors (5556111).

16668321 is an equidigital number, since it uses as much as digits as its factorization.

16668321 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5556110.

The product of its digits is 10368, while the sum is 33.

The square root of 16668321 is about 4082.6855132376. The cubic root of 16668321 is about 255.4449287265. Note that the first 3 decimals are identical.

The spelling of 16668321 in words is "sixteen million, six hundred sixty-eight thousand, three hundred twenty-one".