Chapter 1 - Sections 1.1-1.8 - Exercises - Problems by Topic - Page 40: 78e

There is one significant figure in 2000.

Any non-zero numbers are significant (so the 2 in this case) but the zeroes are insignificant because it could just as easily be re-written as $2 \times 10^{3}$ (which eliminates the insignificant figures)