Plot[40000.  Sin[x], {x, -3 Pi, 3 Pi}, 
     Ticks -> {{-Pi, 0, Pi}, 
               {#, ScientificForm@#} & /@ {-40000., 40000., 10000.}}]

![enter image description here][1]


  [1]: https://i.sstatic.net/nYv6d.png