16666321 has 6 divisors (see below), whose sum is σ = 19387410. Its totient is φ = 14285376.

The previous prime is 16666319. The next prime is 16666343. The reversal of 16666321 is 12366661.

It can be written as a sum of positive squares in only one way, i.e., 10595025 + 6071296 = 3255^2 + 2464^2 .

It is not a de Polignac number, because 16666321 - 2¹ = 16666319 is a prime.

It is not an unprimeable number, because it can be changed into a prime (16666361) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 170016 + ... + 170113.

It is an arithmetic number, because the mean of its divisors is an integer number (3231235).

Almost surely, 2^16666321 is an apocalyptic number.

It is an amenable number.

16666321 is a deficient number, since it is larger than the sum of its proper divisors (2721089).

16666321 is an equidigital number, since it uses as much as digits as its factorization.

16666321 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 340143 (or 340136 counting only the distinct ones).

The product of its digits is 7776, while the sum is 31.

The square root of 16666321 is about 4082.4405690714. The cubic root of 16666321 is about 255.4347115348.

The spelling of 16666321 in words is "sixteen million, six hundred sixty-six thousand, three hundred twenty-one".