【解析】從簡單的入手,尋找規(guī)律
如9×9=81,積的各位數(shù)字之和是8+1=9,每個因數(shù)中有1個9,積的各位數(shù)字之和是1個9;
99×99=9801,積的各位數(shù)字之和是9+8+1=18,每個因數(shù)中有2個9,積的各位數(shù)字之和是2個9;
999×999=998001,積的各位數(shù)字之和是9+9+8+1=27,每個因數(shù)中有3個9,積的各位數(shù)字之和是3個9;
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故所求原式的各位數(shù)字上之和就是2011個9,即9×2011=18099