因数有：1,2,3,4,5,6,8,9,10,12,15,16,18,20,24,30,36,40,45,48,60,72,80,90,120,144,180,240,360,720.
与5互质的有：
2,3,4,6,8,9,12,16,18,24,36,48,72,144,.