It would be great to have a phone number stated in a task and have the ability to click on the number and pull up the phone application to begin the dialing process. Other apps recognize that a phone number is a phone number and present it as a hyperlink which will open the phone app systematically to begin the dialing process.
I use tasks often and put the phone number in but have to open up the task for editing, select the text that is just the phone number, copy the phone number, open up the phone app dial pad and then paste the copied phone number text into the phone app dial pad window.