#include<stdio.h> 
#include<conio.h> 

void main(void) 
{ 
int idem=0,n,dv,lc,ktra; 
printf("Ban nhap n = "); 
scanf("%d",&n); 
lc=n%10; 
ktra=n; 
while(n!=0) 
{ 
dv=n%10; 
if(dv>=lc) 
lc=dv; 
n=n/10; 
} 
while(ktra!=0) 
{ 
dv=ktra%10; 
if(lc==dv) 
idem++; 
ktra=ktra/10; 
} 
printf("Ket qua %d",idem); 
getch(); 
}

#include<conio.h>
 #include<math.h>
 
 int nguyento(int n)
 
 {
 		int i;
 		for (i=2;i<=sqrt(n);i++)
 		if(n%i==0) 
		return 0;
 		return 1;
 
 }
 
 
 void main()
 {
 		int b,a,i;
 		printf("\n Nhap a=");
 		scanf("%d",&a); 
 		while (a!=0) 
 		{
  		b=a%10;
 		a=a/10;
 		if(nguyento(b))
 		printf("%d ",b);//neu nhap 123456 in ra 1,2,3,5 la so nguyen to thi cau lenh in la the nao?
  		}
		printf("la so nguyen to");
		getch();
  }