16721668517 has 2 divisors, whose sum is σ = 16721668518. Its totient is φ = 16721668516.

The previous prime is 16721668501. The next prime is 16721668619. The reversal of 16721668517 is 71586612761.

It is a happy number.

16721668517 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 9794269156 + 6927399361 = 98966^2 + 83231^2 .

It is a cyclic number.

It is not a de Polignac number, because 16721668517 - 2⁴ = 16721668501 is a prime.

It is a super-2 number, since 2×16721668517² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (16721638517) 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, 8360834258 + 8360834259.

It is an arithmetic number, because the mean of its divisors is an integer number (8360834259).

Almost surely, 2^16721668517 is an apocalyptic number.

It is an amenable number.

16721668517 is a deficient number, since it is larger than the sum of its proper divisors (1).

16721668517 is an equidigital number, since it uses as much as digits as its factorization.

16721668517 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 846720, while the sum is 50.

The spelling of 16721668517 in words is "sixteen billion, seven hundred twenty-one million, six hundred sixty-eight thousand, five hundred seventeen".