Is radical 27 a rational or iffational number

Radical 27 is an irrational number and here's why.

Radical 27 can be simplified to 3 radical 3, or 3 times radical 3.
Since radical 3 is an irrational number, as you can see by typing it into a calculator, multiplying it by 3 would still result in a irrational number.

Hope this helps!