diff --git a/src/multiplication.c b/src/multiplication.c
index d6ba3fa..398b12e 100644
--- a/src/multiplication.c
+++ b/src/multiplication.c
@@ -219,7 +219,7 @@ float power_multi(float base, int exponent) {
     return result;
 }
 
-int bitwise_multi(int num1, int num2) {
+int bitwisee_multi(int num1, int num2) {
     int result = 0;
     while (num1) {
         if (num1 & 1) {
@@ -255,6 +255,10 @@ int karatsuba_multi(int num1, int num2) {
     return ac * (int)pow(10, 2 * m2) + ad_bc * (int)pow(10, m2) + bd;
 }
 
+int multiply_by_riesel_prime(int num) {
+    return (num << 2) + (num << 3) - (num << 1) - num;
+}
+
 
 
 
diff --git a/src/multiplication.h b/src/multiplication.h
index 2e9abdb..547ebe3 100644
--- a/src/multiplication.h
+++ b/src/multiplication.h
@@ -30,8 +30,9 @@ int fibonacci_multi(int num, int fib);
 int repeated_division_multi(int num1, int num2);
 int bernoulli_multi(int num, int bernoulli);
 float power_multi(float base, int exponent);
-int bitwise_multi(int num1, int num2);
+int bitwisee_multi(int num1, int num2);
 int karatsuba_multi(int num1, int num2);
+int multiply_by_riesel_prime(int num);