16856921 has 2 divisors, whose sum is σ = 16856922. Its totient is φ = 16856920.

The previous prime is 16856897. The next prime is 16856977. The reversal of 16856921 is 12965861.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 16483600 + 373321 = 4060^2 + 611^2 .

It is an emirp because it is prime and its reverse (12965861) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-16856921 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (16856621) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 8428460 + 8428461.

It is an arithmetic number, because the mean of its divisors is an integer number (8428461).

Almost surely, 2^16856921 is an apocalyptic number.

It is an amenable number.

16856921 is a deficient number, since it is larger than the sum of its proper divisors (1).

16856921 is an equidigital number, since it uses as much as digits as its factorization.

16856921 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 25920, while the sum is 38.

The square root of 16856921 is about 4105.7180857921. The cubic root of 16856921 is about 256.4047602924.

The spelling of 16856921 in words is "sixteen million, eight hundred fifty-six thousand, nine hundred twenty-one".