The 72nd from 101...............as in just counting 3 digit primes........since there are 143 3 digit primes....................an odd number of primes.......................................509 is the median prime.....just counting 3 digit primes..........5 + 0 + 9 = 14.............like 14i.......and a zero..........71 primes on either side.............................- 71 and + 71......................2 71's........like e..............AND 1/2 the square root of 2.............rounded up is 0.71.........+ and -.......two of them..............put together like e and a zero.