[math-fun] about bugs in mathematica and pari-gp

Hello, here is a strange bug, type Prime[8200000000] or Prime[93000000000] in mathematica and your machine will hang forever.... and by a bizarre coincidence, the same thing happens with pari-gp with the value prime(8200000000), I could not test 93 000 000 000 because it is out of reach for pari-gp (I think). Does anybody has any idea why the programs are bugging on these particular values ? Best regards and have a nice day. Simon Plouffe