Same here. I entered 電話番号 and was marked wrong. I don't understand why Duo deems kanji characters acceptable for some words but not the others, especially when doing writing exercises like this.
Is asking someone what their "bangou" alone the same as saying "what's your number" in English?
I don't know if people will understand that as telephone number implicitly, but 番号 is a general enough term that 背番号 means an athlete's jersey number (sebangou, or "back number").
As long as I remember, yes. (although I just failed because I chose only bangou alone)
Interesting that "phone" isn't a loanword (I think, anyway)... Does anyone know the etymology?
電 is the kanji for electricity (e.g. 電車= train) and 話 is used for speech or talking (話す = to talk)
This is the Chinese form for phone number 电话号码. 号 appears in both languages, but its means "month's day or size" in Chinese, instead in Japanese means "issue". I have read anywhere both are intelligebly but sometimes each languages behave different, even coming from the same origin.