16716721 has 4 divisors (see below), whose sum is σ = 19104832. Its totient is φ = 14328612.

The previous prime is 16716709. The next prime is 16716727. The reversal of 16716721 is 12761761.

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 16716721 - 2¹³ = 16708529 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (16716727) 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, 1194045 + ... + 1194058.

It is an arithmetic number, because the mean of its divisors is an integer number (4776208).

Almost surely, 2^16716721 is an apocalyptic number.

It is an amenable number.

16716721 is a deficient number, since it is larger than the sum of its proper divisors (2388111).

16716721 is an equidigital number, since it uses as much as digits as its factorization.

16716721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2388110.

The product of its digits is 3528, while the sum is 31.

The square root of 16716721 is about 4088.6086875611. The cubic root of 16716721 is about 255.6919359506.

The spelling of 16716721 in words is "sixteen million, seven hundred sixteen thousand, seven hundred twenty-one".