How do I change my recovery number?
Trying to change my recovery number where the security code is being sent to. How?
System Preferences/iCloud/Keychain/Options.
On your device, go to Settings → iCloud → Keychain and switch Keychain off then on again.
Tap "Approve with Security Code", tap "Forgot Code" and then tap "Reset".
Follow the instructions to reset iCloud keychain and create a new passcode.
You will then be prompted to update to your new number.
Learned from Zinacef