diff --git a/Cargo.toml b/Cargo.toml
index db939dc..b77b96a 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -1,7 +1,7 @@
 [package]
 name = "plexcryptool"
 authors = ["Christoph J. Scherr <software@cscherr.de>"]
-version = "0.2.5"
+version = "0.2.7"
 edition = "2021"
 readme = "README.md"
 description = "Various tools for use with math and cryptology, includes executable and a library."
diff --git a/src/cplex/cli.rs b/src/cplex/cli.rs
index 9e5d807..7e69baa 100644
--- a/src/cplex/cli.rs
+++ b/src/cplex/cli.rs
@@ -70,8 +70,12 @@ pub enum MathActions {
     Modred(ModredArgs),
     /// p minus 1 prime test
     Pm1(PM1Args),
-    //// calculate in a gallois field
+    /// calculate in a gallois field
     Gallois(GalloisAction),
+    /// Euklidian Algorithm
+    Gcd(GcdArgs),
+    /// factorize a natural number
+    Factorize(FactorizeArgs)
 }
 
 #[derive(Args, Clone, Debug, PartialEq, Eq)]
@@ -105,6 +109,25 @@ pub struct GalloisAction {
     pub action: GalloisActions
 }
 
+#[derive(Args, Clone, Debug, PartialEq, Eq)]
+pub struct GcdArgs {
+    #[clap(value_parser=maybe_hex::<u128>)]
+    /// first number
+    pub a: u128,
+    #[clap(value_parser=maybe_hex::<u128>)]
+    /// second number
+    pub b: u128,
+    #[arg(short, long, default_value_t = false)]
+    /// use extended gcd
+    pub ext: bool
+}
+
+#[derive(Args, Clone, Debug, PartialEq, Eq)]
+pub struct FactorizeArgs {
+    #[clap(value_parser=maybe_hex::<u128>)]
+    pub n: u128,
+}
+
 #[derive(Subcommand, Clone, Debug, PartialEq, Eq)]
 pub enum GalloisActions {
     /// draw the root of n
diff --git a/src/cplex/printing.rs b/src/cplex/printing.rs
index 505fa32..00dbb4a 100644
--- a/src/cplex/printing.rs
+++ b/src/cplex/printing.rs
@@ -138,10 +138,10 @@ pub fn proc_vec<T>(vec: Vec<T>, args: Cli)
         seperator();
     }
     if args.machine {
-        println!("{:#?}", vec);
+        println!("{:?}", vec);
     }
     else {
-        println!("result is\n{:#?}", vec);
+        println!("result is\n{:?}", vec);
     }
 }
 
diff --git a/src/lib.rs b/src/lib.rs
index 23dd9cd..4819520 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -52,6 +52,9 @@ fn register_math_module(py: Python, parent_module: &PyModule) -> PyResult<()> {
     let math_module = PyModule::new(py, "math")?;
     math_module.add_function(wrap_pyfunction!(math::modexp::py_modular_exponentiation, math_module)?)?;
     math_module.add_function(wrap_pyfunction!(math::pm1::py_p_minus_one, math_module)?)?;
+    math_module.add_function(wrap_pyfunction!(math::gcd::gcd, math_module)?)?;
+    math_module.add_function(wrap_pyfunction!(math::gcd::egcd, math_module)?)?;
+    math_module.add_function(wrap_pyfunction!(math::factorise::prime_factors , math_module)?)?;
     parent_module.add_submodule(math_module)?;
     Ok(())
 }
diff --git a/src/main.rs b/src/main.rs
index b336675..2e993cd 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -77,6 +77,20 @@ pub fn main() {
                         }
                     }
                 }
+                MathActions::Factorize(fac_args) => {
+                    let vec = math::factorise::prime_factors(fac_args.n, args.verbose);
+                    cplex::printing::proc_vec(vec, args);
+                }
+                MathActions::Gcd(gcd_args) => {
+                    if gcd_args.ext {
+                        let vec = math::gcd::egcd(gcd_args.a, gcd_args.b);
+                        cplex::printing::proc_vec(vec, args)
+                    }
+                    else {
+                        let num = math::gcd::gcd(gcd_args.a, gcd_args.b);
+                        cplex::printing::proc_num(num, args)
+                    }
+                }
             }
         }
         Commands::Binary(action) => {
diff --git a/src/math/factorise.rs b/src/math/factorise.rs
new file mode 100644
index 0000000..244aec7
--- /dev/null
+++ b/src/math/factorise.rs
@@ -0,0 +1,38 @@
+#![allow(dead_code)]
+/// factorize a large integer
+///
+/// Author:     Christoph J. Scherr <software@cscherr.de>
+/// License:    MIT
+/// Source:     <https://git.cscherr.de/PlexSheep/plexcryptool/>
+
+use pyo3::prelude::*;
+
+#[pyfunction]
+/// find the prime factors of n
+pub fn prime_factors(mut n: u128, verbose: bool) -> Vec<u128> {
+    let mut i: u128 = 2;
+    let mut factors: Vec<u128> = Vec::new();
+    while i.pow(2) <= n {
+        if n % i > 0 {
+            i += 1;
+        }
+        else {
+            n = n.checked_div(i).expect("n / i is not an integer");
+            factors.push(i);
+        }
+        if verbose {
+            println!("i={i}\t{:?}", factors);
+        }
+    }
+    if n > 1 {
+        factors.push(n);
+    }
+    return factors;
+}
+
+#[test]
+fn test_prime_factors() {
+    assert_eq!(prime_factors(360, true), vec![2, 2, 2, 3, 3, 5]);
+    // see https://math.tools/numbers/prime-factors/3603234
+    assert_eq!(prime_factors(3603234, true), vec![2, 3, 223, 2693]);
+}
diff --git a/src/math/gcd.rs b/src/math/gcd.rs
new file mode 100644
index 0000000..54d203c
--- /dev/null
+++ b/src/math/gcd.rs
@@ -0,0 +1,30 @@
+#![allow(dead_code)]
+/// euclidian algorithm, find greatest common divider
+///
+/// This does not implement the euclidian algorithm by itself.
+///
+/// Author:     Christoph J. Scherr <software@cscherr.de>
+/// License:    MIT
+/// Source:     <https://git.cscherr.de/PlexSheep/plexcryptool/>
+
+use num::Integer;
+
+use pyo3::prelude::*;
+
+#[pyfunction]
+/// extended euclidian algorithm
+pub fn egcd(mut a: u128, mut b: u128) -> Vec<i128> {
+    if a > b {
+        let tmp = a;
+        a = b;
+        b = tmp;
+    }
+        let egcd = (a as i128).extended_gcd(&(b as i128));
+        return vec![egcd.gcd, egcd.x, egcd.y]
+}
+
+#[pyfunction]
+/// euclidian algorithm
+pub fn gcd(a: u128, b: u128) -> u128 {
+    a.gcd(&b)
+}
diff --git a/src/math/mod.rs b/src/math/mod.rs
index 3c829fa..e36eccf 100644
--- a/src/math/mod.rs
+++ b/src/math/mod.rs
@@ -10,3 +10,5 @@ pub mod modexp;
 pub mod pm1;
 pub mod modred;
 pub mod gallois;
+pub mod gcd;
+pub mod factorise;