Text To Number

The text to number module provide a widget to number fields then it applies text input into that number field and the
validation hook that will run before save.

Features

You want to add text in to your integer field and have it parsed to integer or NULL? Select this widget in your field display. This will enable people to add text like "No value" or "Missing" but have that turned to NULL rather than zero.

Post-Installation

After installing this module go to the manage form display of your content type and you will find the text to number widget for number fields of that content type.