555

Not sure what you want with "555"—the number, or something around the 555 timer IC? Here are quick facts about the decimal number in case that’s useful for exams:

• Decimal properties: 555 is a repdigit and a palindrome.
• Factorization: 555 = 3 × 5 × 37.
• Divisibility: divisible by 3 and 5; not divisible by 9 or 11.
• Bases:
  • Binary: 555 = 1000101011₂
  • Octal: 555 = 1053₈
  • Hexadecimal: 555 = 0x22B
• Roman numeral: DLV
• Alternate representation: 555 = 15 × 37
• Clock/time cue: 5:55

If you meant the 555 timer IC (electronics), I can give a quick refresher on its operation modes (astable, monostable, bistable), key equations (frequency/period in astable, trigger/threshold levels), and typical circuits. Which would you like to focus on?