555

Here are a few quick exam-relevant facts about the number 555. Tell me which topic you want to dive into or if you meant something else (e.g., 555 timer IC, area code, etc.).

Math basics

• Prime factorization: 555 = 3 × 5 × 37
• Divisors: 1, 3, 5, 15, 37, 111, 185, 555 (8 divisors)
• Sum of divisors: σ(555) = (1+3)(1+5)(1+37) = 912
• Sum of proper divisors: 912 − 555 = 357
• Euler’s totient: φ(555) = 288
• Binary: 555₂ = 1000101011
• Hexadecimal: 0x22B
• Roman numerals: DLV
• Nature: 555 is a deficient number (sum of proper divisors < number)

Optional quick problems you can try

• Prove 555 is not prime using its factorization.
• List all divisors and verify the sum of divisors.
• Compute 555 mod various bases (e.g., mod 7, mod 9).

If you meant something else by 555 (like the 555 timer IC in electronics), I can cover the relevant formulas and typical circuit configurations. Which topic should I focus on?