555

Could you tell me what you want about 555? It could mean different things in different subjects. Here are quick possibilities to choose from or spark ideas:

• Math (number properties)

  • 555 = 3 × 5 × 37
  • Not prime; divisible by 3 and 5
  • Roman numeral: DLV
  • Digit sum = 15

• Electronics (555 timer IC)

  • Astable mode:
    • t_high = 0.693 (R1 + R2) C
    • t_low = 0.693 R2 C
    • f = 1 / [0.693 (R1 + 2R2) C]
    • Duty cycle D = (R1 + R2) / (R1 + 2R2)
  • Monostable mode: t = 1.1 R C

• Other

  • Thai slang for laughter (555 = haha)
  • Fictional US 555 numbers used in media

Tell me the subject and the exact problem or question, and I’ll help you work through it.