How to Standardize WhatsApp Number Format? E.164 Cleaning Order and Special Rules for Argentina and Mexico

WhatsApp requires the full international format: country code + area code + local number, with leading zeros and all symbols removed. This article explains the actual order for list processing: removing symbols, removing trunk prefixes, adding country codes, country-specific corrections (Argentina add 9 remove 15, Mexico add 1), deduplication and grouping, and which number ranges cannot register WhatsApp anyway—so format issues aren't mistaken for invalid numbers.