555

Do you mean one of these, or something else with “555”?

• The number 555 (math facts)
• The 555 timer IC (electronics)
• Something else (e.g., meme, area code)

If you meant the number 555:

• Factorization: 555 = 3 × 5 × 37 (three distinct primes)
• Divisors: 1, 3, 5, 15, 37, 111, 185, 555 (8 divisors)
• Sum of divisors (including itself): 912; sum of proper divisors: 912 − 555 = 357
• Euler totient φ(555) = 288
• Digital root: 5+5+5 = 15 → 1+5 = 6
• In bases: binary 1000101011, octal 1053, hex 0x22B
• Roman numeral: 555 = DLV
• Properties: a repdigit in base 10; odd, composite, and a deficient number (sum of proper divisors 357 < 555)

If you meant the 555 timer IC:

• 8-pin DIP package; key pins typically: GND, Vcc, TRIG, THR, DIS, OUT, RESET, CTRL
• Main configurations:
  • Monostable: one-shot pulse on trigger; T ≈ 1.1 × R × C
  • Astable: free-running oscillator; f ≈ 1.44 / [(R1 + 2R2) × C]; duty cycle ≈ (R1 + R2) / (R1 + 2R2)
• Common uses: timers, programmable delays, PWM signals, square/RC waveforms

Tell me which one you want, or share the exact context, and I’ll tailor the help.