555

Do you mean math (number 555) or electronics (555 timer)? Here are quick math notes you can use for exam prep:

• Prime factorization: 555 = 3 × 5 × 37
• Number of divisors: (1+1)(1+1)(1+1) = 8 Divisors: 1, 3, 5, 15, 37, 111, 185, 555
• Sum of divisors: (1+3)(1+5)(1+37) = 4 × 6 × 38 = 912
• Harshad number (divisible by sum of digits): 555 ÷ (5+5+5 = 15) = 37
• Binary: 555 = 1000101011₂

If you want, I can give you a small practice problem, or switch to 555 timer basics (monostable/astable formulas). What would you prefer?