Integrate[
      Integrate[((1 - a x - b y)/c), {y, 0, ((1 - a x)/b)}], {x, 0, 
        1/a}]

Integrate[
Integrate[
Integrate[
          1 - z, {z, 0, 1 - x - y}] , 
{y, 0, 
          1 - x}], 
{x, 0, 1}]

PrimeQ[20100519]

FactorInteger[20100519]