If 50% of a radioactive element remains after 4000 years what is its half-life?

Half-life (abbreviated t 1⁄2) is the time required for a quantity to reduce to half its initial value. The term is commonly used in nuclear physics to describe how quickly unstable atoms undergo, or how long stable atoms survive, radioactive decay. since it reduce to half after 4000 years, so the half life is 4000 years