555

Do you want something specific about 555, or should I just cover a few quick possibilities?

Here are some quick facts you might find useful for exam prep:

• Math (number theory)

  • Prime factorization: 555 = 3 × 5 × 37
  • Divisibility: divisible by 3 (sum of digits = 15) and by 5 (ends with 5)
  • Binary: 555 = 1000101011₂
  • Hex: 0x22B
  • Roman numerals: DLV
  • In words: five hundred fifty-five

• Electronics (555 timer IC)

  • The 555 timer can be wired in astable (free-running) or monostable (one-shot) configurations
  • Key pins: TRIG (pin 2), THRS (pin 6), DIS (pin 7), OUT (pin 3), RESET (pin 4), VCC (pin 8), GND (pin 1)
  • Astable gives a continuous square wave; frequency f ≈ 1.44 / ((R1 + 2R2) C) for standard configurations
  • Monostable gives a single pulse with width t ≈ 1.1 RC

If you tell me which topic you’re studying (math, electronics, etc.), I can give a targeted explanation or work through an example.