digits, as all irrational numbers do). Often 3.14 is used in numerical calculations, i.e. 3 significant decimal digits, with 7 correct binary digits (while the more accurate 22/7 is also used, even though it also only amounts to the same 3 significant correct decimal digits, it has 10 correct binary digits), which is a good enough approximation for many practical uses. Most calculators, and computer programs, can handle 3.141592653589793, 16 decimal digits, that is commonly used in computers and used by NASA for "JPL's highest accuracy calculations, which are for interplanetary navigation". For "the largest size there is: the visible universe [..] you would need 39 or 40 decimal places." The Planck constant is and is defined as an exact value so that it is more properly defined as . Ways to denote significant figures in an integer with trailing zeros The significance of trailing zeros in a number not containing a decimal point can be ambiguous. For example, it may not always be clear if the number 1300 is precise to the nearest unit (just happens coincidentally to be an exact multiple of a hundred) or if it is only shown to the nearest hundreds due to rounding or uncertainty. Many conventions exist to address this issue. However, these are not universally used and would only be effective if the reader is familiar with the convention: An overline, sometimes also called an overbar, or less accurately, a vinculum, may be placed over the last significant figure; any trailing zeros following this are insignificant. For example, 130 has three significant figures (and hence indicates that the number is precise to the nearest ten). Less often, using a closely related convention, the last significant figure of a number may be underlined; for example, "1300" has two significant figures. A decimal point may be placed after the number; for example "1300." indicates specifically that trailing zeros are meant to be significant. As the conventions above are not in general use, the following more widely recognized options are available for indicating the significance of number with trailing zeros: Eliminate ambiguous or non-significant zeros by changing the unit prefix in a number with a unit of measurement. For example, the precision of measurement specified as 1300 g is ambiguous, while if stated as 1.30 kg it is not. Likewise 0.0123 L can be rewritten as 12.3 mL Eliminate ambiguous or non-significant zeros by using