約數(shù)和質(zhì)數(shù)都是在正整數(shù)范圍里面定義的.質(zhì)數(shù)又叫素數(shù).質(zhì)數(shù)是指約數(shù)只有1和它本身的數(shù).質(zhì)數(shù)的個數(shù)是無限的.質(zhì)因數(shù)即約數(shù)：一個合數(shù)的因數(shù),而且這些因數(shù)都是質(zhì)數(shù).約數(shù)是指能夠整除原來數(shù)的所有整數(shù),叫做這個數(shù)的約數(shù)....