Why can't I save an emergency phone number in my addressbook? I live in Thailand, and the emergency medical response number to dial here is 1669.

When I try to save this number in my address book on Android, it says "Emergency Number Cannot Be Saved". 

What gives? It's probably the most important number for me to save, and I can't. Is there any way to fix this?


My device isn't rooted. 
I'm saving to an address book that is synced via CardDAV.
I'm running Android 8.0.0 on a Xiaomi Mi A1.
The solution that worked was to use a browser on my computer to save the number in the addressbook instead of using the Android contacts app. I used Fastmail, but I expect Google contacts would work in the same way. This then syncs to the phone via CardDAV. After testing it, the number is synced and functional.