Is it possible to cast an NSInteger to NSNumber?

You cannot cast it because NSInteger is not an object, just an alias for a built-in type. You can always create a new NSNumber object from NSInteger, like this:

NSNumber *myNum = @(myNsIntValue);

or in the prior version of the compiler, use

NSNumber *myNum = [NSNumber numberWithInteger:myNsIntValue];

since Apple LLVM Compiler 4.0, there is an easier way to create NSNumber object:

NSNumber *x = @1234; 
NSNumber *y = @(anIntegerVariable);