555

Do you want help with 555 as a number (math) or the 555 timer IC in electronics? Here are quick options to get you started.

If math:

• Factorization: 555 = 3 × 5 × 37
• Divisible by: 3 (since 5+5+5=15) and by 5
• Roman numerals: DLV
• Binary: 555 = 1000101011₂
• In words: five hundred fifty-five
• Quick note: 555 is not prime (has factors 3, 5, 37)

If electronics (555 timer):

• Modes: astable (free-running), monostable (one-shot)
• Astable timing: f ≈ 1.44 / ((RA + 2 RB) C); T ≈ 0.693 (RA + 2 RB) C
• Monostable timing: t ≈ 1.1 × R × C
• Thresholds: 2/3 Vcc (upper) and 1/3 Vcc (lower)
• Pin 5 (control) can decouple/adjust the reference

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