Concept:Number of digits of N is 1 more than the characteristic of log10N.Explanation:Let x=21070.Take log10 on both sides:log10x=log10(21070).Using the power rule, log10x=1070log102.Substitute log102=0.3010:log10x=1070×0.3010=322.07.The characteristic is 322.Thus, number of digits =322+1=323.Answer:The number of digits in 21070 is 323.