555

Do you want something about the number 555, or about the 555 timer IC, or something else?

Here are quick facts in case you need them:

• Prime factorization: 555 = 3 × 5 × 37
• Roman numeral: DLV
• Binary: 1000101011
• Hex: 0x22B
• Sum of digits: 15; digital root: 6

If you meant the 555 timer IC (common in exams on electronics), I can cover:

• Astable frequency formula: f ≈ 1.44 / [(R_A + 2R_B) C]
• Duty cycle considerations and how to get ~50% with diodes or a transistor tweak
• A worked example with chosen resistor and capacitor values

Which would you like?