If you look it up you will find that some sources tell you that for a value with no decimal point, zeros to the right of the rightmost non-zero digit are place holders and do not count as significant digits. Other sources (including several mainstream introductory physics textbooks) state that such zeroes may or may not be significant; such a value by itself does not tell you how many significant digits it contains. Prof. Parodi of the Saint Anselm College Chemistry Department has pointed out that if some accepted sources consider the number of significant digits in a number, that ends in one or more zeroes and has no decimal point, to be ambiguous, then it is ambiguous. In other words, when you see such a value, in the absence of other information (such as words explicitly stating how many significant digits the value has) you have no way of knowing whether the writer was adhering to the "don't count the trailing zeros" rule or the "the number of significant digits is ambiguous rule." In the absence of such information, the number of significant digits in a number, that ends in one or more zeroes and has no decimal point, is indeed ambiguous.