ORDER: phone number as required formula field

[MarthaLouisa]

User Story: As a Product Owner I would like for countries outside of the EU in the checkout the phone number as a required field in the form, because the phone number is for certain carrier a crucial details for the delivery.

Question: Is it possible for Paypal and Paypal express to set the phone number as a mandatory field? If so how does the integration work. 

Shopsystem: Magento 2 

[MTS_Justin]

Hi,

To require that your customer add their phone number when checking out with PayPal Express:

Log in to your PayPal account at paypal.com.

Click My Account.

Click Profile.

Click My selling tools:

In Selling online > Website preferences, click Update.

In Contact Telephone Number, choose an option for Contact Telephone:

On (Optional Field) - adds the phone number field to your checkout but it is not required for checking out.
On (Required Field) - requires that your customer enter their phone number when checking out.
Requiring a phone number on checkout usually decreases conversions and sales. Many people don't like to give out contact information. Unless you absolutely need the phone number, you should choose On (Optional Field).