To validate and look up phone numbers in Google Spreadsheets, you can use the Twilio Phone Number Lookup API. First, sign up for a free trial account with $20 in credit to play with, and then create a new spreadsheet with columns for phone number, status, phone type, carrier, country code, and national format. Use Apps Script to write a lookup function that takes a phone number as input and makes an HTTP GET request to the Twilio API to retrieve information about the phone number, including its status, carrier, name, country code, and national format. The script can then iterate through each phone number in the spreadsheet, look up its details using the lookup function, and update the corresponding columns with the retrieved data. With this setup, you can easily validate and clean up phone numbers, as well as format them properly for use in your application.