Assuming the full stops are thousand separators, the answer is 4 significant digits. However, integers ending in zero are ambiguous.
4
Five. All nonzero digits are significant and zeros in between significant digits are significant.
It has two significant digits.
3 significant digits.
It has 3 significant digits.
4 significant digits.
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.
000203 has 3 significant digits.
Three significant digits.
There are 3 significant digits in 20.0