555

Do you mean:

• The number 555 (math), or
• The 555 timer IC in electronics for circuits?

If you meant the number 555:

• factors: 3 × 5 × 37
• Roman numeral: DLV
• Binary: 1000101011 (decimal 555)
• Hex: 0x22B
• 555^2 = 308,025
• 555 is odd; sum of digits = 15 (divisible by 3 and 5)

If you meant the 555 timer IC:

• Pinout (NE555): 1 GND, 2 Trigger, 3 Output, 4 Reset, 5 Control, 6 Threshold, 7 Discharge, 8 Vcc
• Astable mode: f = 1 / [0.693 C (RA + 2RB)]
  • t_high = 0.693 (RA + RB) C
  • t_low = 0.693 RB C
  • Duty cycle = (RA + RB) / (RA + 2RB)
• Monostable mode: T = 1.1 RC (one-shot)
• Common specs: supply 4.5–16 V; output can source/sink ≈ 200 mA
• Typical uses: oscillators, timing delays, PWM, pulse generation

Tell me which one you want, and I can work through a problem or provide a quick cheat sheet tailored to that topic.