16904815721 has 2 divisors, whose sum is σ = 16904815722. Its totient is φ = 16904815720.

The previous prime is 16904815693. The next prime is 16904815723. The reversal of 16904815721 is 12751840961.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 10478388496 + 6426427225 = 102364^2 + 80165^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-16904815721 is a prime.

Together with 16904815723, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (16904815723) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 8452407860 + 8452407861.

It is an arithmetic number, because the mean of its divisors is an integer number (8452407861).

Almost surely, 2^16904815721 is an apocalyptic number.

It is an amenable number.

16904815721 is a deficient number, since it is larger than the sum of its proper divisors (1).

16904815721 is an equidigital number, since it uses as much as digits as its factorization.

16904815721 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 120960, while the sum is 44.

The spelling of 16904815721 in words is "sixteen billion, nine hundred four million, eight hundred fifteen thousand, seven hundred twenty-one".