555

Do you want something about the number 555, or are you thinking of the 555 timer circuit in electronics? Here are quick math notes in case you meant the number:

• Value: 555 is odd, ends in 5, so divisible by 5.
• Prime factorization: 555 = 3 × 5 × 37.
• Divisibility: divisible by 3 and 5 (and thus by 15); not divisible by 9.
• Decimal properties: palindrome (reads the same forward/backward).
• Roman numeral: DLV.
• Binary: 555 = 1000101011₂.
• Hexadecimal: 555 = 0x22B.
• Squares and cubes: 555² = 308,025; 555³ = 170,953,875.
• Related trick: 555 = 15 × 37, since 555 = 3 × 5 × 37.

If you meant the 555 timer, I can give you the standard formulas for astable and monostable modes. Which direction would you like?