Log in to Pipedrive CRM -> Go to Contacts
Hover your cursor on the number.
Check this Image for your reference:
Valid number-
If you hover over the number, it will show your number as “valid” in green color, which means your number is valid and you can call that number.
Invalid Number-
If you hover over the number and it will show “invalid” in red colour, which means that your number is invalid and you can’t call this number.