In this series odd terms are cubes of odd numbers starting from 1. While even terms are squares of the even numbers starting from 2. Following this pattern we can clearly see that the question mark is replaced with 5^3 = 125.

1 = 1×1×1 4 = 2×2 27= 3×3×3 16 = 4×4 125=5×5×5 36 = 6×6 343=3×3×3

So The required number is 125

Alternating squares and cubes, 125.

Find the number that comes next in the following series:

3, 7, 12, 14, 16, 19, 21, 25, 30, 41, 45, 52, 54, 56, 59, 61, 65, 70, ?