There is one signature figure in the number 1.
1 of them.
1
Seven
1 of them.
1 of them.
1 of them.
1 of them.
1
1
The number of significant figures is one.
1 of them.
Seven
1 of them.
1 of them.
The number 20000 only has 1 significant figure.
6 significant figures.
2 of them.