555

Do you want help with the number 555 (math), or something else like the 555 timer IC, Roman numerals, etc.?

If you meant math, here are quick facts and a couple of practice questions:

• Factorization: 555 = 3 × 5 × 37
• Divisibility: divisible by 3 and 5; digits sum to 15, digital root 6
• Roman numeral: 555 = DLV
• Example problem: Solve 3x + 37y = 555 in integers.
  • Mod 3: 37y ≡ 0 (mod 3) → y ≡ 0 (mod 3) → y = 3t
  • Then 3x + 37(3t) = 555 → x = 185 − 37t
  • Integer solutions: (x, y) = (185 − 37t, 3t) for any integer t
  • Nonnegative solutions (x ≥ 0, y ≥ 0) occur for t = 0,1,2,3,4:
    • (185, 0), (148, 3), (111, 6), (74, 9), (37, 12)

If you meant the 555 timer IC or another context, tell me and I’ll tailor the notes.