Answer:
123,876.3 = 7 sig figs
1,236,840= 7 sig figs
422000 = 3 sig figs
0.000000000000211= 3 sig figs
0.000238 = 3 sig figs
0.0000205 = 3 sig figs
Explanation:
Leading zeros are not significant, trailing zeros with no decimal are not significant. Whole numbers are always significant.