A long number, or virtual mobile number, is a standard-length phone number used as an SMS sender so that recipients can reply, rented per country from a gateway.
A long number looks like an ordinary mobile number and behaves like one for messaging: it can send, receive replies and be saved in a contact list. It is the practical way to get two-way traffic in a country without a short code, and the only way in markets where alphanumeric names are replaced.
Numbers are national, so a campaign to ten countries that needs replies needs ten numbers. Where only one-way traffic is needed, a shared numeric sender assigned by the gateway does the job at no cost.
At SMSMeteor: a two-way number can be added per destination on a campaign; without it, the platform assigns a shared numeric sender automatically where names are not delivered.