Magic Numbers

Seven is the most familiar,
but three is the most mythological.
However, we tend not to remember
forty, which in Middle Eastern cultures
meant 'many'.  Forty days and forty nights
in Biblical wilderness... forty thieves 
which reminds me of delightfully-simple
counting-systems which ran : one, two, three,
four, five, many (or a lot).
No need to get your head
round megawatt.