First, let me remind my readers that a quadrillion is a million billion, or a thousand trillion.
First, let's look at the national debt now (November 1, 2020). According to The Balance, the national debit is currently $22.719 trillion and was $5.656 trillion in 1999.
Over that 20-year period, the debt has grown at a rate of 7.2% per year. At that rate, the debt will reach one quadrillion dollars in the year 2073.