You could try a Fermi approximation: There are 10 billion people * 100 uC chips / person * 10 years of life / uC chip * 10^13 microseconds / year * 1 clock cyc

You could try a Fermi approximation: There are 10 billion people * 100 uC chips / person * 10 years of life / uC chip * 10^13 microseconds / year * 1 clock cycle / microsecond = ~10^26 clock cycles