555

Do you mean:

• the number 555 (quick facts or practice problems), or
• a specific problem labeled "555" in your notes, or
• the Thai slang "555" (laughing)?

If you meant the number 555:

• Prime factorization: 555 = 3 × 5 × 37
• Number of divisors: 8 (1, 3, 5, 15, 37, 111, 185, 555)
• Euler’s totient: φ(555) = 288

Would you like 2-3 quick exam-style problems using 555?