509..................is the 72nd prime with 3 digits...................5 + 9 = 14 and a zero...........14i.......also...........the prime immediately before it is 503...............right after it is 521.......both add up to 8..........adding their digits together.............5 +  0 + 3 = 8................5 + 2 + 1 = 8.............8 + 8 = 16......like the golden ratio...