You have about 100 trillion somatic cells (p. 78), all derived from a single zygote by mitosis.

Each round of mitosis produces 2 daughter cells:

• 10 rounds gives 2¹⁰ = 1024 cells, about 1 thousand.
• 20 rounds gives 2²⁰ = 1,048,576, about 1 million
• 30 rounds gives 2³⁰ = 1,073,741,824, about 1 billion.
• 40 rounds gives 2⁴⁰ = 1,099,511,627,776, about 1 trillion.
• 7 more rounds gives 2⁷ = 128 additional multiplier.

So, your average cell has divided 46-47 times since the zygote stage to reach 100 trillion.

This calculation does not include gametes: eggs and sperm.

Due to telomere shortening, humans have a "Hayflick limit" of about 50 cell divisions (p. 170).