Rate of cell division in humans
My first thought was this:

According to Wikipedia (citation provided)


  Between 50 and 70 billion cells die each day due to apoptosis in the average human adult. For an average child between the ages of 8 and 14, approximately 20 billion to 30 billion cells die a day.


For every cell that dies a new one must be born, so there must be at least between 50 and 70 billion cell divisions to replenish these cells in an adult human (no net growth).

But then I remembered erythrocytes. Wikipedia again:


  Adult humans have roughly 2–3 × 1013 (20–30 trillion) red blood cells at any given time, comprising approximately one quarter of the total human body cell number


and...


  these cells live in blood circulation for about 100 to 120 days


So approximately 1% of erythrocytes are destroyed every day and must be replaced. That's 2-3 x 1011 cells formed every day, which dwarfs the cells replenished due to apoptosis (5 - 7 x 109). 


  Through this process [erythropoiesis] erythrocytes are continuously produced in the red bone marrow of large bones, at a rate of about 2 million per second in a healthy adult.