555

Could you clarify what you want with 555? Here are a few common possibilities. Tell me which subject or ask for something else.

• Math/number theory:

  • 555 = 3 × 5 × 37; divisible by 3, 5, and 15; number of divisors = 8.
  • Roman numeral: 555 = DLV.

• Electronics:

  • 555 timer IC basics (astable/monostable), with quick formulas:
    • Astable: f ≈ 1.44 / ((R1 + 2R2) C) t_high = 0.693 (R1 + R2) C t_low = 0.693 R2 C
    • Monostable: t = 1.1 R C

• Computing/bit-level:

  • 0x555 = decimal 1365; binary pattern 0101 0101 0101 (12 bits).

If you want, I can give you a short practice problem for any of these topics.