There are approximately 5,000 trillion mitochondria in the human body.
"And there's about 5,000 trillion mitochondria in your body." (said at 0:01:04)
No peer-reviewed biomedical publications indexing an exact figure of '5,000 trillion' (or 5 quadrillion) mitochondria in the human body were identified in PubMed. While rough back-of-the-envelope calculations multiplying the number of nucleated cells in the human body (~5-10 trillion, excluding anucleated erythrocytes) by typical mitochondrial content per cell (hundreds to thousands) yield numbers in the low quadrillions (thousands of trillions), this specific estimate has not been formally quantified or established in the indexed scientific literature.