Salesforce: Validation Rule to Control Number Field

Scenario:

To make sure that users do not key in any alphabet values to a field.

Problem:

In some situation, you will need to choose text field type for your number field. For example, Contact_Id__c should be a number field. But if you choose the field type as Number, you will end up having result of ‘100,569,333’ as your Id.

Solution:

To overcome this, you can choose to use text field type. However, you will need some validation to avoid users from adding in alphabet value. For example: