13 sextillion transistors is about 1625 billion transistors per human, though - or just over 200 iPhones' worth of transistors per person. That's still about an order of magnitude higher than I'd have guessed.
A current-gen iPhone SoC (or CPU, the sources are not very clear), nhas about 19 billion transistors. That does not include transistors from flash memory. Following the numbers it does also not include RAM.
IPhone transistor count becomes completely irrelevant when you start looking at flash chips. Even a 16GB flash drive can contain 64 billion transistors.