16321657921 has 2 divisors, whose sum is σ = 16321657922. Its totient is φ = 16321657920.

The previous prime is 16321657909. The next prime is 16321657931. The reversal of 16321657921 is 12975612361.

16321657921 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 15559069696 + 762588225 = 124736^2 + 27615^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-16321657921 is a prime.

It is not a weakly prime, because it can be changed into another prime (16321657931) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 8160828960 + 8160828961.

It is an arithmetic number, because the mean of its divisors is an integer number (8160828961).

Almost surely, 2^16321657921 is an apocalyptic number.

It is an amenable number.

16321657921 is a deficient number, since it is larger than the sum of its proper divisors (1).

16321657921 is an equidigital number, since it uses as much as digits as its factorization.

16321657921 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 136080, while the sum is 43.

The spelling of 16321657921 in words is "sixteen billion, three hundred twenty-one million, six hundred fifty-seven thousand, nine hundred twenty-one".