555

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• The number 555 (math):

  • Prime factors: 3 × 5 × 37
  • Divisors: 1, 3, 5, 15, 37, 111, 185, 555
  • Decimal to other bases: binary 1000101011, hex 0x22B, Roman numeral DLV
  • Sum of digits = 15; divisible by 3 and 5

• The 555 timer IC (electronics):

  • Two main configurations: astable (oscillator) and monostable (one-shot)
  • Astable: frequency f ≈ 1.44 / [(RA + 2RB) · C], duty cycle ≈ (RA + RB) / (RA + 2RB)
  • Monostable: pulse width t ≈ 1.1 · R · C
  • Quick example: RA = 1 kΩ, RB = 10 kΩ, C = 100 nF → f ≈ 1.44 / [(1k + 20k)·100nF] ≈ 686 Hz; t ≈ 1.1 × 10 kΩ × 100 nF ≈ 1.1 ms

If you tell me which context you want, I can go deeper or solve a specific problem.