The following are basic rules for significant figures.
Non-zero number are significant
Examples:
8794 has four significant figures
54 has two significant figures
2 has one significant figure
Zeros between significant digits are significant
Examples:
105 has three significant figures
1.05 has three significant figures
Zeros to the right of the decimal point and to the right of a non-zero digit are significant.
Examples
0.0105 has three significant figures
3.450 has four significant figures
520 has two significant figures