555

Could you clarify what you want with "555"? Here are a few quick options:

• Math/number properties: factors (555 = 3 × 5 × 37), bases (binary 1000101011, hex 0x22B, octal 1053), Roman numeral (DLV), divisibility (divisible by 3, 5, 15, 37, 111, etc.).
• Electronics: the 555 timer IC — how it works in astable/monostable modes, formula for frequency and timing.
• Other: any specific calculation or topic related to 555.

Tell me which you’d like, and I’ll dive in.