Quire, ream, bundle & bale

25 sheets = 1 quire

500 sheets = 20 quires = 1 ream

1,000 sheets = 40 quires = 2 reams = 1 bundle

5,000 sheets = 200 quires = 10 reams = 5 bundles = 1 bale

See more at http://en.wikipedia.org/wiki/Units_of_paper_quantity