Usage of "Number"

“Number”

Number: Use number to refer to quantities that can be counted.

Incorrect: The amount of microprocessors manufactured in 2003 was more than that manufactured in 2002.
Correct: The number of microprocessors manufactured in 2003 was more than that manufactured in 2002.

Here, microprocessor is a countable noun, i.e., it can be counted, and should used with the word “number.”