Let's denote the unknown number as \( x \).
According to the statement, one third of the number is twelve. We can express this mathematically as:
\[ \frac{1}{3}x = 12 \]
To find \( x \), we need to multiply both sides of the equation by 3:
\[ x = 12 \times 3 \]
Calculating that gives:
\[ x = 36 \]
So the number is 36.
If you have any specific operation or application in mind regarding addition, subtraction, multiplication, or division with this number, please let me know!