Question

在小于1100的正整数中，有多少个数有偶数个因数？

Answer 1

1-1099里面，总共有1066个是，33个不是，不是的分别是：
1的因数为:1
4的因数为:1,2,4
9的因数为:1,3,9
16的因数为:1,2,4,8,16
25的因数为:1,5,25
36的因数为:1,2,3,4,6,9,12,18,36
49的因数为:1,7,49
64的因数为:1,2,4,8,16,32,64
81的因数为:1,3,9,27,81
100的因数为:1,2,4,5,10,20,25,50,100
121的因数为:1,11,121
144的因数为:1,2,3,4,6,8,9,12,16,18,24,36,48,72,144
169的因数为:1,13,169
196的因数为:1,2,4,7,14,28,49,98,196
225的因数为:1,3,5,9,15,25,45,75,225
256的因数为:1,2,4,8,16,32,64,128,256
289的因数为:1,17,289
324的因数为:1,2,3,4,6,9,12,18,27,36,54,81,108,162,324
361的因数为:1,19,361
400的因数为:1,2,4,5,8,10,16,20,25,40,50,80,100,200,400
441的因数为:1,3,7,9,21,49,63,147,441
484的因数为:1,2,4,11,22,44,121,242,484
529的因数为:1,23,529
576的因数为:1,2,3,4,6,8,9,12,16,18,24,32,36,48,64,72,96,144,192,288,576
625的因数为:1,5,25,125,625
676的因数为:1,2,4,13,26,52,169,338,676
729的因数为:1,3,9,27,81,243,729
784的因数为:1,2,4,7,8,14,16,28,49,56,98,112,196,392,784
841的因数为:1,29,841
900的因数为:1,2,3,4,5,6,9,10,12,15,18,20,25,30,36,45,50,60,75,90,100,150,180,225,300,450,900
961的因数为:1,31,961
1024的因数为:1,2,4,8,16,32,64,128,256,512,1024
1089的因数为:1,3,9,11,33,99,121,363,1089