How to calculate the angle for the phasor form?
Yes, the magnitude of the current is 23.72 amps.
To calculate the phase angle, the easiest way is to convert the rectangular impedance to a magnitude (already done) and an angle. The angle is \$\arctan(4/2)\$ = 63.435 °.
Given that it is a positive value, when you divide voltage (at 0 °) by an impedance having an angle of +63.435 ° the net result for current is a negative angle of 63.435 °