diff --git a/code_study/Baekjoon/c/11653.c b/code_study/Baekjoon/c/11653.c
new file mode 100644
index 0000000..447de3a
--- /dev/null
+++ b/code_study/Baekjoon/c/11653.c
@@ -0,0 +1,20 @@
+#include <stdio.h>
+
+int main() {
+    int N;
+    scanf("%d",&N);
+
+    int v=2;
+    if(N==1) printf("1");
+    while(v<=N) {
+        if(N%v==0) {
+            printf("%d\n",v);
+            N/=v;
+        }
+        else {
+            v++;
+        }
+    }
+
+    return 0;
+}
\ No newline at end of file
diff --git a/code_study/Baekjoon/c/1978.c b/code_study/Baekjoon/c/1978.c
new file mode 100644
index 0000000..e242868
--- /dev/null
+++ b/code_study/Baekjoon/c/1978.c
@@ -0,0 +1,27 @@
+#include <stdio.h>
+
+int main() {
+    int N, count=0;
+    int arr[100];
+    scanf("%d",&N);
+    for(int i=0; i<N; i++){
+        scanf("%d",&arr[i]);
+    }
+
+    for(int i=0; i<N; i++){
+        if(arr[i]==1){
+            count++;
+            continue;
+        }
+        for(int j=2; j*j<=arr[i]; j++){
+            if(arr[i]%j==0){
+                count++;
+                break;
+            }
+        }
+    }
+
+    printf("%d",N - count);
+
+    return 0;
+}
\ No newline at end of file
diff --git a/code_study/Baekjoon/c/2501.c b/code_study/Baekjoon/c/2501.c
new file mode 100644
index 0000000..0adae6d
--- /dev/null
+++ b/code_study/Baekjoon/c/2501.c
@@ -0,0 +1,18 @@
+#include <stdio.h>
+
+int main() {
+    int n, k, temp=1;
+    scanf("%d %d",&n,&k);
+    while(k && temp<=n) {
+        if(n%temp==0) {
+            k--;
+        }
+        if(k==0) break;
+        temp++;
+    }
+
+    if(k==0) printf("%d",temp);
+    else printf("0");
+
+    return 0;
+}
\ No newline at end of file
diff --git a/code_study/Baekjoon/c/2581.c b/code_study/Baekjoon/c/2581.c
new file mode 100644
index 0000000..af2b93d
--- /dev/null
+++ b/code_study/Baekjoon/c/2581.c
@@ -0,0 +1,31 @@
+#include <stdio.h>
+
+int main() {
+    int m, n;
+    scanf("%d",&m);
+    scanf("%d",&n);
+
+    int isPrime;
+    int sum=0, min=0;
+
+    for(int v=m; v<=n; v++) {
+        if(v==1) continue;
+
+        isPrime=1;
+        for(int i=2; i*i<=v; i++) {
+            if(v%i==0){
+                isPrime=0;
+                break;
+            }
+        }
+        if(isPrime) {
+            if(min==0) min=v;
+            sum+=v;
+        }
+    }
+
+    if(sum==0) printf("-1");
+    else printf("%d\n%d",sum, min);
+
+    return 0;
+}
\ No newline at end of file
diff --git a/code_study/Baekjoon/c/5086.c b/code_study/Baekjoon/c/5086.c
new file mode 100644
index 0000000..2bf4fce
--- /dev/null
+++ b/code_study/Baekjoon/c/5086.c
@@ -0,0 +1,16 @@
+#include <stdio.h>
+
+int main() {
+    int a, b;
+    
+    while(1) {
+        scanf("%d %d",&a, &b);
+        if ( a==0 && b==0 ) break;
+
+        if (a%b==0) printf("multiple\n");
+        else if (b%a==0) printf("factor\n");
+        else printf("neither\n");
+    }
+    
+    return 0;
+}
\ No newline at end of file
diff --git a/code_study/Baekjoon/c/9506.c b/code_study/Baekjoon/c/9506.c
new file mode 100644
index 0000000..8b0a5b3
--- /dev/null
+++ b/code_study/Baekjoon/c/9506.c
@@ -0,0 +1,32 @@
+#include <stdio.h>
+
+int main() {
+    int n, sum, len;
+    while(1){
+        scanf("%d",&n);
+        if(n==-1) break;
+
+        sum=1;
+        len=0;
+        int fac[36] = {1,};
+        for(int i=2; i<=n/2; i++){
+            if(n%i==0) {
+                sum+=i;
+                fac[++len]=i;
+            }
+        }
+
+        if(sum==n){
+            printf("%d = 1",n);
+            for(int i=1; i<=len; i++) {
+                printf(" + %d",fac[i]);
+            }
+        }
+        else {
+            printf("%d is NOT perfect.",n);
+        }
+        printf("\n");
+    }
+
+    return 0;
+}
\ No newline at end of file