The $$2's$$ complement representation of $${\left( { - 539} \right)_{10}}$$ in hexadecimal is

Zero has two representations in:

Given $$\sqrt {\left( {224} \right),} = {\left( {13} \right)_r},$$
The value of the radix' $$r$$ is:

Consider the number given by the decimal expression.
$${16^3} \times 9 + {16^2} \times 7 + 16 \times 5 + 3$$

The number of $$1's$$ in the unsigned binary representation of the number is _______.