555

Could you tell me what you want about 555? math, electronics (555 timer), or something else?

Quick notes you might find useful:

• Math: 555 = 3 × 5 × 37. Divisors: 1, 3, 5, 15, 37, 111, 185, 555. It’s a palindrome and a Harshad number (555 ÷ (5+5+5) = 37).
• Electronics (555 timer IC): A versatile timer IC. In astable mode: f ≈ 1 / [0.693 × (RA + 2RB) × C], duty cycle D ≈ (RA + RB) / (RA + 2RB). In monostable mode: the output pulse width t ≈ 1.1 × R × C (with R and C set by external components).

Tell me which topic (or a different one) you want help with, and I’ll dive in.