3.774 is to 4 significant figures (count them)
4 significant figures.
There are two types of significant figures, measured and exact. Numbers are often rounded to avoid reporting insignificant figures. Numbers can also be rounded merely for simplicity rather than to indicate a given precision of measurement.
All three of them are significant figures
The number of significant figures should be equal to the significant figures in the least precise measurement.
28.71
642000 expressed as four significant figures is 6.420e5
significant figures.
4
Four, assuming that 7.000 is written in that form to indicate that it has 4 significant figures.
I know what I believe you to be talking about by another name: Significant figures. Significant figures like decimal points, but they are measured from the front of a number e.g. 3.1234567 to 4 significant figures would be: 3.123
Significant figures indicate the precision of a measurement.
If you have written a number such as 111.1 to 3 significant figures, for example, (which would be 111) then we would write "111 (to 3 s.f.)".