takuhaibokkusu no bangou wo wasureta node, kanrigaisya ni denwasimasita.

宅配ボックス means a parcel locker or delivery box, usually the kind found in an apartment building or condo. Delivery companies can leave packages there when you are not home.

In this sentence, it most likely refers to the building’s package locker system, not just a cardboard box.

Yes, 番号 literally means number, but in context it can mean things like:

• a locker number
• an access number
• a PIN/code

So even though the word is simply number, the natural English meaning may be something like the code for the parcel locker or the locker number, depending on the situation.

The particle の connects two nouns. It often works like of or an apostrophe-s in English.

So:

• 宅配ボックス = parcel locker
• 番号 = number
• 宅配ボックスの番号 = the parcel locker’s number / the number for the parcel locker

This is a very common pattern in Japanese:

• 学校の先生 = the school’s teacher / teacher at the school
• 日本の文化 = Japanese culture / the culture of Japan

Because 番号 is the direct object of 忘れた.

• 忘れた = forgot
• What did the speaker forget?
  → 宅配ボックスの番号

So:

• 宅配ボックスの番号を忘れた = I forgot the parcel locker number/code

The particle を marks the thing that is directly affected by the verb.

Because ので attaches to the plain form of a verb, not the -て form.

So:

• 忘れた = plain past form
• 忘れたので = because I forgot

忘れてので is incorrect.

A quick pattern:

• verb plain present + ので
  行くので = because I will go / because I go
• verb plain past + ので
  行ったので = because I went

ので means because, since, or so. It gives a reason.

Here:

• 宅配ボックスの番号を忘れたので、管理会社に電話しました。
• Because I forgot the parcel locker number, I called the management company.

Compared with から:

• ので sounds a bit softer, more explanatory, and often more polite
• から can sound more direct or more subjective

So in a sentence like this, ので sounds very natural because the speaker is calmly explaining why they called.

Compare:

• 忘れたので、電話しました。
  = Because I forgot it, I called.
• 忘れたから、電話しました。
  = Because I forgot it, I called.

Both are grammatical, but ので sounds slightly gentler and more formal.

This is very common in Japanese.

When a plain-form clause comes before ので, から, けど, と思う, etc., it often stays in plain form even if the main sentence is polite.

So:

• 忘れたので = plain form + ので
• 電話しました = polite main verb

This mixture is completely natural.

You could make the first part more polite in some contexts:

• 宅配ボックスの番号を忘れましたので、管理会社に電話しました。

This sounds more formal. But the original sentence is very normal everyday Japanese.

Because に marks the target of the phone call.

• 管理会社に電話する = to call the management company

With 電話する, the person or place being called is commonly marked with に.

Examples:

• 母に電話する = call my mother
• 会社に電話する = call the company

So here:

• 管理会社に電話しました = I called the management company

Both are possible, but 電話しました is more natural and more common.

That is because 電話する functions like a single verb meaning to call / to make a phone call.

So Japanese often says:

• 友だちに電話した
• 病院に電話した
• 管理会社に電話しました

You may also hear 電話をする, but the version without を is usually smoother in everyday speech.

管理会社 means management company—usually the company that manages an apartment building, condo, or rental property.

In this sentence, it likely means the company responsible for the building where the parcel locker is located. If you forgot the locker number or code, calling them would make sense.

This is different from:

• 不動産会社 = real estate company
• 大家さん = landlord
• 管理人 = building manager/caretaker

Japanese often leaves out information that is clear from context.

So although English would usually say:

• I forgot the parcel locker number, so I called the management company.

Japanese does not need to say 私 unless it is important.

Also, my is not needed before parcel locker number because the context already tells us which number is being talked about.

This omission is very normal in Japanese and can feel strange to English speakers at first.

Yes, but Japanese word order is different from English.

The basic flow is:

1. reason/background
2. main action

So:

• 宅配ボックスの番号を忘れたので = because I forgot the parcel locker number
• 管理会社に電話しました = I called the management company

Japanese verbs usually come at the end of their clause, so 忘れた ends the reason clause and 電話しました ends the full sentence.

Yes, depending on what is actually meant.

• 番号 = number
• 暗証番号 = PIN / passcode / security code

If the parcel locker uses a numeric code, 暗証番号 may be more specific:

• 宅配ボックスの暗証番号を忘れたので、管理会社に電話しました。

That would clearly mean I forgot the parcel locker passcode, so I called the management company.

The original 番号 is broader and may rely on context.

No. In normal Japanese writing, the sentence would usually be written without spaces:

宅配ボックスの番号を忘れたので、管理会社に電話しました。

Spaces are often added in learning materials to make it easier to see the parts of the sentence. That is helpful for beginners, but it is not standard everyday Japanese writing.