555

Not sure what you want about 555. Do you want math, electronics (555 timer), or something else? Here are quick notes in two common topics:

Math

• 555 = 3 × 5 × 37 (prime factorization)
• Number of divisors: (1+1)(1+1)(1+1) = 8
• Sum of divisors: 912 (1+3)(1+5)(1+37) = 4×6×38 = 912
• Binary: 555 = 1000101011
• Roman numerals: DLV

Electronics (555 timer IC)

• Modes: astable (free-running), monostable (one-shot), bistable (flip-flop)
• Astable frequency: f ≈ 1.44 / [(RA + 2 RB) C]
• Duty cycle ≈ (RA + RB) / (RA + 2 RB) × 100%
• Monostable pulse width: T ≈ 1.1 × R × C
• Trigger/threshold levels: 1/3 Vcc and 2/3 Vcc

If you tell me your subject or give a specific problem, I can tailor a detailed, step-by-step solution.