555

Not sure what you want with "555" — math fact, electronics, or something else. Here are quick possibilities you can use as quick-reference or a starting point for exam prep. Tell me which direction you want and I’ll tailor it.

Quick facts about 555:

• Factorization: 555 = 3 × 5 × 37 (prime factors).
• Divisibility: divisible by 3 and by 5 (ends with 5).
• Roman numeral: DLV (500 + 50 + 5).
• Binary: 555 = 1000101011₂.
• Base-3: 555₁₀ = 202120₃.
• Other representations: 555 = 111 × 5 = 37 × 15.
• Digit sum and mod: sum of digits = 15; digital root = 6; 555 mod 9 = 6.
• If you’re studying electronics (555 timer): in astable mode, f ≈ 1.44 / ((R_A + 2R_B) C); duty cycle D = (R_A + R_B) / (R_A + 2R_B).

If you meant something else (e.g., the Chinese slang for “crying,” a 555 timer circuit problem, or a specific exam question), tell me and I’ll tailor the help. Do you want a quick practice problem set or a one-page summary for a particular topic?