diff --git a/journal/2023-09-29.md b/journal/2023-09-29.md
index 658c265ea..bcaabdf69 100644
--- a/journal/2023-09-29.md
+++ b/journal/2023-09-29.md
@@ -1,2 +1,7 @@
 - [[29]] is [[drishti]] in the #Flancia [[Pattern Language]].
-- [[209]] is not prime; it is 19 * 11.
+- My hobby: think about whether numbers are prime.
+  - [[209]] is not prime; it is 19 * 11.
+    - I find this one quite beautiful as there are two simple "proofs" to get there:
+      - It is not multiple of two or five trivially.
+      - It is not a multiple of three as its digits don't add up to a multiple.
+  - [[1547]] is not prime; it is 13 * 7 * 17.