Number Needed to Treat

Which of the following statements about the ‘Number Needed to Treat’ are correct?

The ‘Number Needed to Treat’ means ‘How many times would I need to set up Early Goal Directed Therapy to prevent one death?’ in this study
The ‘Number Needed to Treat’ is the inverse of the risk reduction
The ‘Number Needed to Treat’ is the inverse of the absolute risk reduction
The ‘Number Needed to Treat’ varies depending on the death rate in the study
The ‘Number Needed to Treat’ does not vary depending on the death rate in the study