Number Series - General Questions

Look at this series and find the number that does not belong: 8, 27, 64, 125, 218, 343, 512

Look at this series and find the number that does not belong: 2, 6, 18, 54, 160, 486, 1458

Look at this series and find the number that does not belong: 5, 5, 9, 15, 25, 40, 65

Look at this series: 51, 56, 61, 66, 71, 76, … What number should come next?

Look at this series: 134, 122, 110, 98, 86, 74, … What number should come next?