一个自然数把各位数倒过来仍是本身,这个数为回文数,如606 ,90509求从1到1000000有多少回文数?怎么求?

在自然数中,最小的回文数是0,其次是1,2,3,4,5,6,7,8,9,11,22,33,44,55,66,77,88,99,101,111,121,131,141,151,161,171,181,191,202,212,222,232,242,252,262,272,282,292,303,313,323,333,343,353,363,373,383,393,404,414,424,434,444,454,464,474,484,494,505,515,525,535,545,555,565,575,585,595,606,616,626,636,646,656,666,676,686,696,707,717,727,737,747,757,767,777,787,797,808,818,828,838,848,858,868,878,888,898,909,919,929,939,949,959,969,979,989,999.
1000000/10*9=900000个

1位数都是，1到9就9个
2位数AA形式，9个
3位数ABA形式，9*10=90个
4位数ABBA形式，9*10=90个
5位数ABCBA形式，9*10*10=900个
100000不是
综上，从1到100000
9*2+90*2+900=1098个