To find out what fractional part 660 is of 660,000, you can set up the fraction:
\[ \text{Fraction} = \frac{660}{660,000} \]
Now, we simplify the fraction. Both the numerator and the denominator can be divided by 660:
\[ \frac{660 \div 660}{660,000 \div 660} = \frac{1}{1000} \]
So, 660 is \(\frac{1}{1000}\) of 660,000.