555

Do you mean the number 555 in math, the 555 timer IC in electronics, or something else? Here are quick notes for both:

Math (555)

• Factorization: 555 = 3 × 5 × 37
• Divisors: 1, 3, 5, 15, 37, 111, 185, 555 (eight divisors)
• It’s a Harshad (Niven) number: 555 ÷ (5+5+5) = 37
• Roman numeral: DLV
• Base conversions: binary 1000101011, octal 1053, hex 0x22B
• Decimal properties: palindrome, digital root 6 (sum of digits 15 → 1+5=6)

Electronics (555 timer IC)

• Common IC: NE555, 8-pin DIP
• Major configurations: astable (oscillator) and monostable (one-shot)
• Astable formulas (charging through RA + RB, discharging through RB):
  • t_high = 0.693 (RA + RB) C
  • t_low = 0.693 RB C
  • Frequency ≈ f = 1.44 / [(RA + 2 RB) C]
• Monostable (one-shot) time:
  • t ≈ 1.1 R C
  • Trigger threshold: 1/3 Vcc to start, 2/3 Vcc to end
• Components: RA, RB, C set timing; pin 7 is discharge, pin 2 trigger, pin 6 threshold, etc.

If you tell me which context you’re in (math, electronics, or something else), I can tailor a quick answer or help with a specific problem.