The following are significant digits:
All nonzero digits are significant.
All zeros located between significant digits.
All zeros at the end of the decimal.
All digits of the first factor when a number is expressed in scientific notation.
Underscored or specified zeros of a whole number ending in zeros.

The following are digits that are not significant:
Zeros at the end of a whole number(unless specified to be significant).
Zeros following the decimal point in a number between 0 and 1.