555

Do you want something specific about 555? Here are quick options:

• Math fact: 555 = 3 × 5 × 37. It’s divisible by 3 and 5 (and hence by 15). In other bases: binary 1000101011, octal 1053, hex 0x22B. Not prime.

• Roman numerals: 555 = DLV.

• Electronics (555 timer IC): a common timer circuit. In astable mode, frequency ≈ 1.44 / ((R1 + 2R2)·C); in monostable mode, pulse width t ≈ 1.1·R·C; pinout basics: 1 GND, 2 Trigger, 3 Output, 4 Reset, 5 Control, 6 Threshold, 7 Discharge, 8 Vcc.

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