diff --git a/journal/2023-09-29.md b/journal/2023-09-29.md
index bcaabdf69..e5e8a1065 100644
--- a/journal/2023-09-29.md
+++ b/journal/2023-09-29.md
@@ -4,4 +4,5 @@
     - 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.
+      - It is not a multiple of 7 as 210 is (as 21 is 3 * 7); and it's too near to it.
   - [[1547]] is not prime; it is 13 * 7 * 17.