Can I apply Rice's theorem to decide decidability status of these languages?
You're right that both of these are non-trivial properties. The key is, Rice's theorem applies only to non-trivial semantic properties.

So what defines a semantic property?

Intuitively, a "semantic" property is a property of what the machine does, rather than how the machine works. If you treat the machine as a black box that takes input and gives output, with all the internal mechanisms hidden, semantic properties are the ones you can still measure.

Applying this rule of thumb, we see that printing letters and multiplying numbers are both semantic actions (they're things a program does rather than mechanisms by which the program does it), so yes, Rice's Theorem applies, and these properties are undecidable.