2,001 - Two thousand (and) one 2,015 - Two thousand (and) fifteen 2,134 - Two thousand, one hundred and thirty four In British English, 'and' can be used for hundreds, thousands, millions etc: 342, 455 = three hundred AND forty two thousand, four hundred AND fifty five 105, 342, 455 = one hunded AND five million, three hundred AND forty two thousand, four hundred AND fifty five

In American English, we DO say "Two thousand (and) one" and "Two thousand (and) fifteen". It's optional, but it sounds nice to use "and". However, we say only "Two thousand one hundred and thirty four". We don't use "and" in that case. As Gary said below, that would be too many "and"s and it sounds strange.