这个电话号码是256357，在英语中应该说作 "two-five-six, three-five-seven"。

这种表达方式的来源是因为在英语中，数字都有独特的读音。例如：

"two" 读作 [tu:]
"five" 读作 [faɪv]
"six" 读作 [sɪks]
"three" 读作 [θri:]
"seven" 读作 [ˈsevən]

所以在读电话号码时，我们按照每个数字的读音进行读取。

例如：

"My phone number is two-five-six, three-five-seven." (我的电话号码是256357。)
"Can I have your phone number? It's two-five-six, three-five-seven." (你的电话号码是多少？是256357。)
"The phone number for the customer service department is two-five-six, three-five-seven." (客服部门的电话号码是256357。)