Is there a cheap way to obfuscate a 64bit int?

I'm writing C and C# code (same example, same algorithm, two languages).

I was wondering is there a fast way to obfuscate an int? The fastest way I can think of is newInt = currentInt ^ harcodedNumber. But that's obvious and lame. You'll 100% know the numbers are sequential. The other solution I thought of is newInt = currentInt ^ randomInt ^ harcodedNumber then return both newInt and randomInt. I was wondering if someone could come up with something better?