16684721 has 4 divisors (see below), whose sum is σ = 16896000. Its totient is φ = 16473444.

The previous prime is 16684699. The next prime is 16684747. The reversal of 16684721 is 12748661.

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 16684721 - 2¹⁰ = 16683697 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (16684751) 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, 105521 + ... + 105678.

It is an arithmetic number, because the mean of its divisors is an integer number (4224000).

Almost surely, 2^16684721 is an apocalyptic number.

It is an amenable number.

16684721 is a deficient number, since it is larger than the sum of its proper divisors (211279).

16684721 is an equidigital number, since it uses as much as digits as its factorization.

16684721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 211278.

The product of its digits is 16128, while the sum is 35.

The square root of 16684721 is about 4084.6935013536. The cubic root of 16684721 is about 255.5286788860.

The spelling of 16684721 in words is "sixteen million, six hundred eighty-four thousand, seven hundred twenty-one".