The number 15287 is divisible by which of the following?

The correct answer is Option (4) → None of the above

Each divisor has its own test: 3 and 9 need the digit sum divisible by 3 or 9, and 8 needs the number formed by the last three digits divisible by 8.

• Digit sum \(=1+5+2+8+7=23\), which is divisible by neither 3 nor 9, so 15287 is not divisible by 3 or 9

• The last three digits form 287, and \(287=8\times35+7\), so 15287 is not divisible by 8

None of 3, 8 and 9 divides 15287, so the answer is None of the above.