Identify the next number in the Series:

100, 99, 96, 91, 84, 75, 64,_____

The next number in the series is 51.

Here's the reasoning:

• The differences between consecutive numbers are: 1, 3, 5, 7, 9, 11.
• These differences increase by 2 each time.
• Following this pattern, the next difference should be 13.
• Subtracting 13 from the last number (64 - 13) gives 51.

So, the completed series is:
100, 99, 96, 91, 84, 75, 64, 51.