Look at this series: 2, 5, 17, 71 ....... What number should come next?

This series is a pattern of multiplication and addition. Here's how you can figure it out:

1. Start with 2.
2. Multiply by 2 and then add 1 to get 5.
3. Multiply by 3 and then add 2 to get 17.
4. Multiply by 4 and then add 3 to get 71.

Following this pattern, the next step would be to multiply 71 by 5 and then add 4.

So, 71 * 5 = 355, and 355 + 4 = 359.

Therefore, the next number in the series should be 359.