16691321 has 2 divisors, whose sum is σ = 16691322. Its totient is φ = 16691320.

The previous prime is 16691317. The next prime is 16691347. The reversal of 16691321 is 12319661.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 16687225 + 4096 = 4085^2 + 64^2 .

It is an emirp because it is prime and its reverse (12319661) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 16691321 - 2² = 16691317 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (16691371) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 8345660 + 8345661.

It is an arithmetic number, because the mean of its divisors is an integer number (8345661).

Almost surely, 2^16691321 is an apocalyptic number.

It is an amenable number.

16691321 is a deficient number, since it is larger than the sum of its proper divisors (1).

16691321 is an equidigital number, since it uses as much as digits as its factorization.

16691321 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1944, while the sum is 29.

The square root of 16691321 is about 4085.5013156282. The cubic root of 16691321 is about 255.5623677313.

The spelling of 16691321 in words is "sixteen million, six hundred ninety-one thousand, three hundred twenty-one".