Is it rational or irrational?

It is an irrational number.

Irrational numbers can be written as a decimal but not a fraction. It has an endless non-repeating digits to the right of the decimal point.

Rational numbers are those that can be written as a ratio. Meaning it can be written as a fraction where both numerator and denominator are whole numbers.

√6 = 2.449489742783

Is a irrational number, because an irrational number is a number that con ONLY be written as a decimal, and not as a ratio/fraction and this number CAN'T be written as a ration/fraction.

On the other hand rational means that a number can be written as a ratio/fraction AND a decimal. 

So, this is an irrational number. 

Hope I helped ya