555

Do you want math-focused info about the number 555, or something else (e.g., a different context or a quick problem)? If you’re prepping for exams, here are some quick, useful facts and a couple of practice prompts.

Key facts about 555 (math)

• Factorization: 555 = 3 × 5 × 37
• Divisors: 1, 3, 5, 15, 37, 111, 185, 555 (8 divisors)
• Sum of divisors: σ(555) = 912
• Euler’s totient: φ(555) = 288
• Divisibility: digits sum is 15 → divisible by 3; last digit 5 → divisible by 5; hence divisible by 15; 555/15 = 37
• Binary: 555 = 1000101011₂
• Base 3: 555 = 202120₃

Simple exam-style practice

• Practice 1: Verify the factorization and list all divisors. Answer: 555 = 3 × 5 × 37; divisors listed above.
• Practice 2: Compute gcd and lcm with 1000.
  • gcd(555, 1000) = 5
  • lcm(555, 1000) = (555 × 1000) / 5 = 111,000
• Practice 3: Compute φ(555).
  • φ(555) = 555 × (1 − 1/3) × (1 − 1/5) × (1 − 1/37) = 555 × (2/3) × (4/5) × (36/37) = 288

If you want, tell me your preferred topic (factorization, modular arithmetic, base conversions, etc.), and I’ll tailor a quick set of exam-style problems.