2. The largest natural number that cannot be expressed as the sum of four distinct composite numbers is $\qquad$ .

翻译完成，保留了原文的格式和换行。
2. 26 .

The sum of the four smallest composite numbers is $4+6+8+9=27$. It is easy to prove that any natural number greater than 27 can be expressed as the sum of four different composite numbers.