555

Not sure what you want with “555.” Do you mean:

• math properties of the number 555
• the 555 timer IC (electronics)
• something else (e.g., Roman numeral DLV, Thai texting slang, etc.)

If you want a quick starter, here are a few options:

1. Math properties of 555

• Factors: 555 = 3 × 5 × 37
• Divisible by: 3, 5, 15 (sum of digits is 15)
• Palindrome and odd; not prime
• 555² = 308,025
• In binary: 555 = 1000101011₂
• Roman numeral: DLV

2. 555 timer IC (electronics)

• Used to generate precise delays and oscillations (monostable, astable, bistable)
• Key formulas (typical configurations):
  • Astable: f ≈ 1.44 / [(RA + 2RB) · C]
    • t_high ≈ 0.693 · (RA + RB) · C
    • t_low ≈ 0.693 · RB · C
  • Monostable: t ≈ 1.1 · R · C (triggered by a pulse)
• Pinout (common DIP8): 1 GND, 2 TRIG, 3 OUT, 4 RESET, 5 CTRL, 6 THR, 7 DISCH, 8 VCC
• Great for practice problems on timing, PWM, and RC networks

3. Other meanings (Roman numerals, Thai slang, etc.)

Tell me which interpretation you want and the level of detail (quick overview or full worked problems), and I’ll tailor it to your exam prep.