Time-based One-Time Password (TOTP) token services rely on the physical device - i.e. your smartphone - rather than a phone number. In particular, they protect your account against SIM cloning. In addition to the benefits of increased security, TOTP has the ability to work without an internet connection and offers users the flexibility to choose from a range of authentication applications like Google Authenticator, Microsoft Authenticator, Authy, 1Password, LastPass, and more.
Learn more about the Authenticator Apps available with TOTP.