In written numbers, there are a few rules that determine which digits are considered significant figures, also known as significant digits.

1. Any non-zero number is significant.
2. Any zero located between non-zero numbers is significant.
3. Trailing zeros at the end of a number are only significant when there is a decimal point.
4. Zeros to the left of the first nonzero digit are not significant.

Below are some examples.

Number	Significant Figures	Comment
$123$	$1,$ $2,$ and $3$	All digits are non-zero.
$1.0002$	$1,$ $0,$ $0,$ $0,$ and $2$	The zeros are between non-zero numbers.
$2.00$	$2,$ $0,$ and $0$	There is a decimal point.
$0.012$	$1$ and $2$	The zeros are to the left of the first non-zero digit.

Significant figures indicate a value's accuracy, with more significant figures indicating a higher degree of accuracy.

Integers Ending with Zero(s)

For an integer that ends with one or more zeros, the trailing zero(s) may or may not be significant figures. In the case of the integer $6700,$ there are multiple possible numbers of significant figures. To avoid uncertainty in such situations, either a decimal point placed at the end of the number or scientific notation should be used.