How many significant figures does the number 12 have

It has 2.

Step-by-step explanation:

Since the numbers aren't zeroes they are automatically significant figures.

2

Step-by-step explanation:

There are 2 digits needed to nail down the precise value of 12: a 1 in the tens place and a 2 in the ones place, giving it 2 significant figures.

For a few more examples, the number 1.23 would have 3 significant figures, the number 56.89 would have 4, and the number 1.00000 would have 1, as the trailing zeroes don't contribute anything to the number's actual value.