how to express (5 x 5.4 10-3) in objective-c

I am trying to convert from meter to nautical miles. I need to multiply met开发者_StackOverflow中文版ers by 5.4x10^-3 but I am not sure how express this number in objective-c.

Any help would be greatly appreciated,

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Like this:

double factor = 5.4e-3;

This means: 5.4 times 10 to the power -3.