diff --git a/src/context/helper.rs b/src/context/helper.rs
index e3bc871..664fed8 100644
--- a/src/context/helper.rs
+++ b/src/context/helper.rs
@@ -38,6 +38,32 @@ pub fn fix(arg: &Value) -> EvalResult {
 	} else { Err(EvalexprError::wrong_function_argument_amount(1, 2)) }
 }
 
+pub fn greatest_common_divisor(arg: &Value) -> EvalResult {
+	if let Value::Tuple(args) = arg {
+		let len = args.len();
+		if len != 2 { return Err(EvalexprError::wrong_function_argument_amount(len, 2)); }
+
+		let a = args[0].clone();
+		let b = args[1].clone();
+
+		if let (Value::Int(a), Value::Int(b)) = (a, b) { Ok( Value::Int( util::gcd(i64::max(a, b), i64::min(a, b)) ) ) }
+		else { Err(EvalexprError::expected_int( if !args[0].is_int() { args[0].clone() } else { args[1].clone() } )) }
+	} else { Err(EvalexprError::expected_tuple(arg.clone())) }
+}
+
+pub fn least_common_multiple(arg: &Value) -> EvalResult {
+	if let Value::Tuple(args) = arg {
+		let len = args.len();
+		if len != 2 { return Err(EvalexprError::wrong_function_argument_amount(len, 2)); }
+
+		let a = args[0].clone();
+		let b = args[1].clone();
+
+		if let (Value::Int(a), Value::Int(b)) = (a, b) { Ok( Value::Int( util::lcm(i64::max(a, b), i64::min(a, b)) ) ) }
+		else { Err(EvalexprError::expected_int( if !args[0].is_int() { args[0].clone() } else { args[1].clone() } )) }
+	} else { Err(EvalexprError::expected_tuple(arg.clone())) }	
+}
+
 pub fn logarithm(arg: &Value) -> EvalResult {
 	let value: f64;
 	let base: Option<f64>;
diff --git a/src/context/mod.rs b/src/context/mod.rs
index 3023be6..58ccdd1 100644
--- a/src/context/mod.rs
+++ b/src/context/mod.rs
@@ -28,6 +28,8 @@ pub fn build(args: &mut Arguments) -> HashMapContext {
 				//	math functions
 				"cos"	=>	Function::new(|arg| helper::cosine(arg)),
 				"fix"	=>	Function::new(|arg| helper::fix(arg)),
+				"gcd"	=>	Function::new(|arg| helper::greatest_common_divisor(arg)),
+				"lcm"	=>	Function::new(|arg| helper::least_common_multiple(arg)),
 				"log"	=>	Function::new(|arg| helper::logarithm(arg)),
 				"sin"	=>	Function::new(|arg| helper::sine(arg)),
 				"sqrt"	=>	Function::new(|arg| helper::square_root(arg)),
diff --git a/src/util.rs b/src/util.rs
index 6daadbf..c2e1811 100644
--- a/src/util.rs
+++ b/src/util.rs
@@ -1,6 +1,16 @@
 
 use evalexpr::{ EvalexprError, Value };
 
+pub fn gcd(big: i64, small: i64) -> i64 {
+	if small == 0 { big }
+	else { gcd(small, big % small) }
+}
+
+pub fn lcm(big: i64, small: i64) -> i64 {
+	let product = (big * small).abs();
+	product / gcd(big, small)
+}
+
 pub fn parse_radix(prefix: &str, base: u32, arg: &str) -> Result<Value, EvalexprError> {
 	let parse = arg.strip_prefix(prefix).unwrap_or(arg);