-96.84% is the change from 664 to 21
Calculation steps:
[( 21 - 664 ) ÷ 664] x 100 = -96.84%
Formula
Percentage change = [(21 - 664) / 664] x 100
Subtract the new number by the original number
21 - 664 = -643
-643 ÷ 664 = -0.9683734939759037
-0.9683734939759037 x 100 = -96.84%