www.treasurydirect.gov puts the debt at around $17.3 trillion (this will change, so I'm not putting an exact amount).

A related quote from Wikipedia

On December 12, 2013, debt held by the public was approximately $12.312 trillion or about 73% of Q3 2013 GDP[5][6] Intragovernmental holdings stood at $4.9 trillion (29%), giving a combined total public debt of $17.226 trillion or over 100% GDP

Now, the reason I'm doubting this is because of two "dissenters". One says it is $90 trillion UC PROFESSOR PEGS NATIONAL DEBT AT NEARLY $90 TRILLION DOLLARS; and one says the US has a surplus of $1,138.26 trillion

Are either of those correct? The original article that piqued my interest was in Barrons entitled No Accounting for Government Cost.