What number comes next in the series? 7,9,13,21,37, ____?

None of these

The pattern involves differences between consecutive terms:

9 - 7 = 2

13 - 9 = 4

21 - 13 = 8

37 - 21 = 16

The differences follow a sequence: 2, 4, 8, 16... (doubling each time).

Next difference = 16 × 2 = 32.

Next term = 37 + 32 = 69.