"Telephone numbers" are not really numbers in the mathematical sense. They are just addresses (similar to email addresses) that happen to be composed of numeric digits. They do not need to be represented as numbers because typical numeric manipulations are not relevant. For example, it makes no sense to subtract one phone number from another.
Therefore you should store telephone numbers in your tables as strings, not as numbers. In particular, a common
int (signed, 32-bit) could store the phone number
2025551212 with the hyphens removed) but could not store
6135551212 is too large to fit into an
int column. (The largest "number" it could hold would be