thousands of
... hundreds of 数百;数以百计 thousands of 数千;数以千计 hundreds of thousands of 几十万;无数的 ...
by thousands
... by hundreds 数以百计 by thousands 数以千计;大量 by(the) millions 数以百万计 ...
letters by the thousands
Clay Tablet
thousands of people
数以千计,读作 shù yǐ qiān jì,汉语词汇。