In 1 half circle there is 648000000 millisecond of arc.

angular mil [NATO] arc minute arc second binary degree binary radian brad circle cycle degree [°] full circle full turn gon [grad] grad [grad] grade [grad] gradian [grad] half circle hour angle milliarc minute milliarc second millisecond of arc minute of arc [MOA] octant point quadrant radian [rad] revolution [rev] right angle rotation second of arc sextant sign

angular mil [NATO] arc minute arc second binary degree binary radian brad circle cycle degree [°] full circle full turn gon [grad] grad [grad] grade [grad] gradian [grad] half circle hour angle milliarc minute milliarc second millisecond of arc minute of arc [MOA] octant point quadrant radian [rad] revolution [rev] right angle rotation second of arc sextant sign