little unsure on some exponent type math I did...

when I did the volume I took (4/3)(pie)(r)^3 basically just plugged in (1.2X10^-15) into my figures and it kicked out something approaching:

volume = - 2.44 X 10^7

I then divided Mass/Volume:

(1.67X10^-27)/(-2.44X10^7) = 6.84X10^-35

am I using these exponents correctly in scientific notation and getting the approximate right answers?

Thanks

Brian