diff --git a/challenges/euler/package.json b/challenges/euler/package.json
index f2fdb26..3cdb26c 100644
--- a/challenges/euler/package.json
+++ b/challenges/euler/package.json
@@ -14,6 +14,7 @@
         "chalk": "^4.1.2",
         "cheerio": "^1.0.0-rc.10",
         "execution-time": "^1.4.1",
+        "ms": "^2.1.3",
         "regenerator-runtime": "^0.13.9",
         "ts-node": "^10.4.0",
         "typescript": "^4.4.4"
diff --git a/challenges/euler/pnpm-lock.yaml b/challenges/euler/pnpm-lock.yaml
index bf851e9..a78bc21 100644
--- a/challenges/euler/pnpm-lock.yaml
+++ b/challenges/euler/pnpm-lock.yaml
@@ -8,6 +8,7 @@ specifiers:
     chalk: ^4.1.2
     cheerio: ^1.0.0-rc.10
     execution-time: ^1.4.1
+    ms: ^2.1.3
     regenerator-runtime: ^0.13.9
     ts-node: ^10.4.0
     typescript: ^4.4.4
@@ -20,6 +21,7 @@ devDependencies:
     chalk: 4.1.2
     cheerio: 1.0.0-rc.10
     execution-time: 1.4.1
+    ms: 2.1.3
     regenerator-runtime: 0.13.9
     ts-node: 10.4.0_626351e049b80b142acb2ce48a7f5656
     typescript: 4.4.4
@@ -518,6 +520,13 @@ packages:
             }
         dev: true
 
+    /ms/2.1.3:
+        resolution:
+            {
+                integrity: sha512-6FlzubTLZG3J2a/NVCAleEhjzq5oxgHyaCU9yYXvcLsvoVaHJq/s5xXI6/XXP6tz7R9xAOtHnSO/tXtF3WRTlA==
+            }
+        dev: true
+
     /nth-check/2.0.1:
         resolution:
             {
diff --git a/challenges/euler/readme.md b/challenges/euler/readme.md
index 838e4d6..8599d27 100644
--- a/challenges/euler/readme.md
+++ b/challenges/euler/readme.md
@@ -32,7 +32,7 @@ The source code can be found in the [src](src) directory. My thoughts about some
 -   [x] [18 - Maximum path sum I](src/18%20-%20Maximum%20path%20sum%20I.ts)
 -   [x] [19 - Counting Sundays](src/19%20-%20Counting%20Sundays.ts)
 -   [x] [20 - Factorial digit sum](src/20%20-%20Factorial%20digit%20sum.ts)
--   [ ] 21 - Amicable numbers
+-   [x] [21 - Amicable numbers](src/21%20-%20Amicable%20numbers.ts)
 -   [ ] 22 - Names scores
 -   [ ] 23 - Non-abundant sums
 -   [ ] 24 - Lexicographic permutations
diff --git a/challenges/euler/scripts/run.js b/challenges/euler/scripts/run.js
index 26407e1..c96df84 100644
--- a/challenges/euler/scripts/run.js
+++ b/challenges/euler/scripts/run.js
@@ -1,7 +1,8 @@
 const fs = require('fs');
 const chalk = require('chalk');
 const { spawnSync } = require('child_process');
-const perf = require('execution-time')();
+const executionTime = require('execution-time')();
+const ms = require('ms');
 
 const generateBanner = text => {
     // Calculate the length of the divider
@@ -20,42 +21,84 @@ const run = file => {
     console.log(generateBanner(file.split('.ts')[0]));
 
     // Execute the file
-    perf.start();
+    executionTime.start();
+
     spawnSync('npx', ['ts-node', `"src/${file}"`], {
         shell: true,
         stdio: 'inherit'
     });
-    const results = perf.stop();
+
+    const results = executionTime.stop();
 
     // Print time results
     console.log();
     console.log(chalk.bold(chalk.yellow(`Executed in ${results.words}`)));
+
+    return results.time;
+};
+
+const runMany = files => {
+    let totalTime = 0;
+
+    files.forEach(file => {
+        const time = run(file);
+        totalTime += time;
+        console.log();
+    });
+
+    console.log(
+        chalk.magenta(
+            chalk.bold(
+                `This set of executions took roughly ${ms(totalTime, { long: true })} in total!`
+            )
+        )
+    );
 };
 
 // Get files
-const tsFiles = fs
+const allFiles = fs
     .readdirSync('src')
     .filter(f => f.endsWith('.ts'))
     .filter(f => f !== 'utils.ts');
 
 // Extract the puzzle number
-const puzzleNumber = process.argv[2];
+process.argv.shift();
+process.argv.shift();
 
-if (puzzleNumber === 'all' || !puzzleNumber) {
-    tsFiles
-        .sort((a, b) => {
-            a = parseInt(a.split('-')[0]);
-            b = parseInt(b.split('-')[0]);
+if (process.argv[0] === 'all' || process.argv.length === 0) {
+    const files = allFiles.sort((a, b) => {
+        a = parseInt(a.split('-')[0]);
+        b = parseInt(b.split('-')[0]);
 
-            return a > b ? 1 : -1;
-        })
-        .forEach(file => {
-            run(file);
-            console.log();
-        });
-} else if (!isNaN(puzzleNumber)) {
+        return a > b ? 1 : -1;
+    });
+
+    runMany(files);
+} else if (process.argv.length > 1 || process.argv[0].includes(',')) {
+    let puzzleNumbers = process.argv
+        .map(v =>
+            v.includes(',')
+                ? v.split(',').map(e => (!isNaN(e) ? parseInt(e) : null))
+                : !isNaN(v)
+                ? parseInt(v)
+                : null
+        )
+        .flat()
+        .filter(e => e !== null);
+    puzzleNumbers = puzzleNumbers.filter((e, i) => puzzleNumbers.indexOf(e) === i);
+
+    const files = allFiles.filter(f =>
+        f.match(
+            `^(?:[${puzzleNumbers.map((number, i) =>
+                i === puzzleNumbers.length - 1 ? number : `${number}|`
+            )}]) -`
+        )
+    );
+
+    runMany(files);
+} else if (!isNaN(process.argv[0])) {
     // Find the associated puzzle
-    const [file] = tsFiles.filter(f => f.startsWith(puzzleNumber));
+    const [file] = allFiles.filter(f => f.startsWith(process.argv[0]));
     run(file);
 } else {
     console.log(
diff --git a/challenges/euler/src/10 - Sumation of primes.ts b/challenges/euler/src/10 - Sumation of primes.ts
index b6da33e..c954ff8 100644
--- a/challenges/euler/src/10 - Sumation of primes.ts	
+++ b/challenges/euler/src/10 - Sumation of primes.ts	
@@ -4,7 +4,7 @@ export {};
 
 /**
  * Use the Sieve of Eratosthenes to find the sum of primes up until a limit.
- * @see https://github.com/newtykins/the-honk/tree/main/projects/euler/thoughts/10%20-Summation%20of%29primes.md
+ * @see https://github.com/newtykins/the-honk/tree/main/challenges/euler/thoughts/10%20-%20Summation%20of%29primes.md
  */
 const sumOfPrimes = (limit: number) => {
     let array: boolean[] = [];
diff --git a/challenges/euler/src/15 - Lattice paths.ts b/challenges/euler/src/15 - Lattice paths.ts
index 876f9f8..ebfcb72 100644
--- a/challenges/euler/src/15 - Lattice paths.ts	
+++ b/challenges/euler/src/15 - Lattice paths.ts	
@@ -13,7 +13,7 @@ const factorial = (n: number) => {
 
 /**
  * Count the lattice paths using the formula shown in the thoughts document.
- * @see https://github.com/newtykins/the-honk/tree/main/projects/euler/thoughts/15%20-Lattice%20paths.md
+ * @see https://github.com/newtykins/the-honk/tree/main/challenges/euler/thoughts/15%20-%20Lattice%20paths.md
  */
 const countLatticePaths = (width: number, height: number) => {
     return factorial(width + height) / (factorial(width) * factorial(height));
diff --git a/challenges/euler/src/9 - Special Pythagorean triplet.ts b/challenges/euler/src/9 - Special Pythagorean triplet.ts
index 2e4bc93..35d803b 100644
--- a/challenges/euler/src/9 - Special Pythagorean triplet.ts	
+++ b/challenges/euler/src/9 - Special Pythagorean triplet.ts	
@@ -6,7 +6,7 @@ export {};
 
 /**
  * Find a Pythagorean triplet based on its sum
- * @see // See https://github.com/newtykins/the-honk/tree/main/projects/euler/thoughts/9%20-Special%20Pythagorean%29triplet.md
+ * @see https://github.com/newtykins/the-honk/tree/main/challenges/euler/thoughts/9%20-%20Special%20Pythagorean%29triplet.md
  */
 const pythagoreanTriplet = (sum: number) => {
     let a: number,