快速测试：你要添加/减少/乘/除电话号码吗？不。与SSN类似，电话号码是可以包含实际数字的离散数据，因此字符串类型可能是最合适的。

Quick test: are you going to add/subtract/multiply/divide Phone Numbers? Nope. Similarly to SSNs, Phone Numbers are discrete pieces of data that can contain actual numbers, so a string type is probably most appropriate.