1. The problem is to determine which number among 51, 102, 153, 867, or 2601 fits a certain pattern or rule. 2. Since no explicit pattern is given, let's analyze the numbers for common properties such as divisibility, prime factors, or special number types. 3. Check if any number is a perfect square or cube: - $51 = 3 \times 17$, not a perfect square or cube. - $102 = 2 \times 3 \times 17$, not a perfect square or cube. - $153$ is a known Armstrong number: $1^3 + 5^3 + 3^3 = 1 + 125 + 27 = 153$. - $867 = 3 \times 289 = 3 \times 17^2$, not a perfect square or cube. - $2601 = 51^2$, a perfect square. 4. Among these, $153$ is special as an Armstrong number, and $2601$ is a perfect square. 5. If the question is to identify a special number, $153$ stands out as an Armstrong number. 6. Therefore, the answer is $153$.