WhatsApp uses your phone number as the primary identifier for your account. To use WhatsApp, you must register a phone number that you own and can receive SMS or phone calls on for verification purposes. The registration process involves entering your full international phone number (including country code, without leading zeros), then receiving a 6-digit verification code via SMS or phone call to confirm ownership

. Key points about WhatsApp phone numbers:

• You can only register phone numbers you own and can receive SMS or calls on.
• Unsupported numbers include VoIP, toll-free, paid premium, universal access numbers, and landlines (landlines only supported on WhatsApp Business app)

• When changing your WhatsApp phone number, you enter both old and new numbers in full international format, and WhatsApp transfers your account info and chats to the new number

• WhatsApp does not use usernames or logins; your phone number is your identity on the platform

If you have issues registering your number, ensure you use the latest WhatsApp version, have a working internet connection, and enter your number correctly in international format

. For contacting WhatsApp support or help, you can use their official contact forms or reach them through the app's Help section

. In summary, your WhatsApp number is your verified phone number in international format, used to register and identify your account on the platform.