自然数中恰好有4个因数的两位数有多少10,14,15,21,22,26,33,34,35,38,39,46,51,55,57,58,62,65,69,74,77,82,85,86,87,91,93,94,95
2*(5,7,11,13,17,19,23,29,31,37,41,43,47),共有13个;3*(5,7,11,13,17,19,23,29,31),共有9个;5*(5,7,11,13,17,19)共有6个;7*(7,11),共有2个。总共有13+9+6+2=30个