555

Could you tell me what you want with “555”? math, electronics (555 timer), or something else? Here are quick bits for a couple common cases:

• Math/number theory

  • 555 = 3 × 5 × 37
  • Number of divisors: 8
  • Sum of divisors: 912
  • Euler’s totient φ(555) = 288
  • Roman numeral: DLV
  • Binary: 1000101011
  • Hex: 0x22B

• Electronics (555 timer basics)

  • Pinout (typical 8-pin DIP): 1 GND, 2 DIS, 3 CTRL, 4 RESET, 5 THR, 6 OUT, 7 CONT? (depends on variant) and 8 VCC (check your package). The common pins are VCC, GND, THR, TRIG, DIS, OUT, RESET, CTRL.
  • Astable (free-running) frequency: f ≈ 1.44 / ((R1 + 2 R2) C)
    • High time t_high ≈ 0.693 (R1 + R2) C
    • Low time t_low ≈ 0.693 R2 C
  • Monostable (one-shot) pulse width: t ≈ 1.1 R C
  • If you want, I can design a sample circuit for a target frequency and duty cycle and pick component values.

Tell me which topic you’re after, or share a problem you’re stuck on, and I’ll help you work through it.