To display the integer value, MyInteger, inside a Log Message activity, the expression that should be used is:
"The value is" + MyInteger.ToString
This expression uses the string concatenation operator (+) to combine the string literal "The value is" with the string representation of the MyInteger variable. The MyInteger variable is an integer type, which cannot be directly concatenated with a string type. Therefore, the ToString method is used to convert the MyInteger variable to a string type3. For example, if the MyInteger variable has the value 42, then the expression "The value is" + MyInteger.ToString will return the string "The value is 42". The Log Message activity writes the specified message to the Output panel, the log files, and the Orchestrator logs. The Log Message activity has a property called Message, which is the text to be logged4. The expression can be entered in the Message property of the Log Message activity to display the integer value.
References: String Concatenation, Int32.ToString Method, and Log Message from UiPath documentation.