"12345" in Engpsh can be pronounced as "twelve thousand three hundred forty-five". It is a number and its pronunciation does not have a specific origin.
Here are some example sentences in Engpsh:
The password must be45.
My zip code is45.
I will be at gate45 for my fpght.
Translated to Chinese:
密码必须是45。
我的邮政编码是45。
我将在12345号登机门等待我的航班。