printf("n = ? "); fflush(stdin);
scanf("%i",&n);

while(n>0){
	... n/10 ...
	... n%10 ...
}

place[i]	digit[i]=	n%10	n = n/10;	i	freq[i]	digits
十 百 千 萬 十萬 百萬 千萬 億	digit[0] digit[1] digit[2] digit[3] digit[4] digit[5] digit[6] digit[7] digit[8] digit[9]			0 1 2 3 4 5 6 7 8 9

int num, digits[10];
char place[5][5] = {"","十","百","千","萬"};
char unit[10][5] = {"０","一","二","三","四","五","六","七","八","九"};

num2digit.htm