21.58 Megahertz.
50 Hz has an edge over 60 Hz as it will have less skin effect and therefore line resistance will be less. Therefore, voltage drop as well as unwanted loss of energy in the line will be less. That...
Hz = cps = cycles per second Measurement of frequency, named for Heinrich Hertz. -HZ stands for hertz. It is the measurement of frequency.
1/45 sec or 0.023 sec
hertz (the International System of Units base unit of frequency)