555

Do you mean one of these, or something else with "555"?

• Math/number theory: factorization, divisors, Roman numerals, properties of the number 555.
• Electronics: the 555 timer IC (astable/monostable configurations, frequency formulas).
• Other: a problem or dataset labeled 555.

If you want, I can give a quick starter on one of these. For example, math quick facts: 555 = 3 × 5 × 37; divisors: 1, 3, 5, 15, 37, 111, 185, 555; sum of divisors = 912; Roman numeral = DLV. Or tell me your subject and I’ll tailor a problem and solution.