microsoft authenticator asks me to put a number in it when I can't open it yet

Microsoft Authenticator is asking for a number because number matching is enabled for your multifactor authentication (MFA).

With number matching, the sign-in page (in a browser or app) shows a number. At the same time, a push notification is sent to Authenticator on the phone. To approve the sign-in, that same number must be entered in Authenticator. This protects the account from attackers who might try to just tap “Approve” on random prompts.

On the same device (for example, using Outlook, Teams, or Authenticator on the same phone):

1. The app or browser where sign-in started shows a number on the screen.
2. A notification from Authenticator appears on the device.
3. Tapping the notification opens Authenticator, where the number from step 1 is entered or confirmed.

It can feel like Authenticator is “asking for a number before it’s open,” but what’s really happening is:

• The number is displayed in the app or browser where sign-in was started.
• Authenticator opens (from the notification) and waits for that number.
• Switching back to the original app/browser will show the number that needs to be typed into Authenticator.

If the prompt never completes or seems stuck:

• Make sure Authenticator is unlocked and notifications are enabled.
• Confirm the app is up to date and the device has a working network connection.
• If “Authentication did not complete” appears, follow the troubleshooting guidance for that error.

References:

• How number matching works in MFA push notifications for Authenticator - Authentication methods policy
• Authenticator app same-device number matching
• Troubleshoot problems with Microsoft Authenticator