Choose the number which is different from the others.

Looking at each number to identify what makes one different:

Option 1: 295

• Digit sum: $2 + 9 + 5 = 16$

Option 2: 552

• Digit sum: $5 + 5 + 2 = 12$

Option 3: 729

• Digit sum: $7 + 2 + 9 = 18$

Option 4: 906

• Digit sum: $9 + 0 + 6 = 15$

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Checking divisibility by 3:

A number is divisible by 3 if the sum of its digits is divisible by 3.

For 295: $16 \div 3 = 5$ remainder $1$ (not divisible by 3)

For 552: $12 \div 3 = 4$ (divisible by 3)

For 729: $18 \div 3 = 6$ (divisible by 3)

For 906: $15 \div 3 = 5$ (divisible by 3)

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295 is the only number not divisible by 3, making it different from the others.

Therefore, the answer is Option 1: 295.