The current US national debt is $28.9 trillion. In 2020, the total tax revenue collected by the US government from individual income tax returns was $1.6 trillion. Determine N, the number of years it would take to pay off the current national debt if all of the tax revenue from personal income tax returns is applied to the debt each year. Assume that the interest on the debt is 2.1% and that the annual revenue from individual income tax returns remains constant. Note that because individual income tax comprises 47% of the total federal revenue, it would not be realistic to apply all of it the debt as these funds are used primarily for other purposes. The answer is an integer. You must enter the exact answer.