diff --git a/素数判断..cpp b/素数判断..cpp
new file mode 100644
index 0000000..eb730d3
--- /dev/null
+++ b/素数判断..cpp
@@ -0,0 +1,21 @@
+#include<stdio.h>
+#include<math.h>
+ 
+int main()
+{
+    int i, n, k;
+ 
+    scanf("%d", &n);
+    k = sqrt(n + 1);
+ 
+    for(i = 2; i <= k; i++) 
+        if(n % i == 0) 
+            break;
+ 
+    if(i <= k || n == 1)
+        printf("No\n");
+    else
+        printf("Yes\n");
+ 
+    return 0;
+}