How many significant figure

How many significant figure 0' 001

D e a r s t u d e n t I f a n u m b e r i s w r i t t e n i n t h e f o r m a \times 10^{b}, t h e n t h e n u m b e r o f s i g n i f i c a n t d i g i t s i n a \times 10^{b} i s e q u a l t o t h e n u m b e r o f s i g n i f i c a n t d i g i t s i n a . H e r e w e h a v e 0.001 \times 10^{- 1} S e e 0.001 Z e r o s t o t h e l e f t o f f i r s t n o n - z e r o d i g i t a r e i n s i g n i f i c a n t S o i t h a s o n l y o n e s i g n i f i c a n t d i g i t 0.001 \times 10^{- 1} h a s o n l y o n e s i g n i f i c a n t d i g i t .