4
4 significant digits.
It has two significant digits.
It has 3 significant digits.
3 significant digits.
Five. All nonzero digits are significant and zeros in between significant digits are significant.
Five. All nonzero digits are significant and zeros in between significant digits are always significant.
Five. All nonzero digits are significant and zeros in between significant digits are always significant.
Five. All nonzero digits are significant and zeros in between significant digits are always significant.
Six - zeros between significant digits are significant.
5 significant digits.
There are three significant digits in 3.56.