7805
The 7805 is a fixed five-volt linear voltage regulator.
- Odd
- Composite
Where 7805 fits
Why 7805 is special
It wastes the difference between input and output as heat, which is both its great simplicity and the reason switching regulators replaced it in battery equipment.
Factors & digit properties
- Divisors (8)
- 1, 5, 7, 35, 223, 1115, 1561, 7805
- Prime factorisation
- 5 × 7 × 223
- Digit sum
- 20
- Digital root
- 2
Representations
- Decimal
- 7805
- Scientific notation
- 7.805 × 10^3
Roman numerals
Roman numerals as modelled here goes up to 3,999.
Binary
1 1 1 1 0 0 1 1 1 1 1 0 1
1 × 4,096 + 1 × 2,048 + 1 × 1,024 + 1 × 512 + 0 × 256 + 0 × 128 + 1 × 64 + 1 × 32 + 1 × 16 + 1 × 8 + 1 × 4 + 0 × 2 + 1 × 1 = 7,805
Octal
1 7 1 7 5
1 × 4,096 + 7 × 512 + 1 × 64 + 7 × 8 + 5 × 1 = 7,805
Hexadecimal
1 e 7 d
1 × 4,096 + e × 256 + 7 × 16 + d × 1 = 7,805
Read as powers of two: 4,096 + 2,048 + 1,024 + 512 + 64 + 32 + 16 + 8 + 4 + 1 = 7,805.
In historical numeral systems
Egyptian
7 lotuses, 8 coils of rope, 5 strokes
7 × 1,000 + 8 × 100 + 5 × 1 = 7,805. The signs are simply repeated and added; where they sit on the line is a matter of layout, not value.
Systems that simply cannot reach this value are left out. Where a script needs a font most readers do not have, the reading is given instead of the glyphs — see number systems for each system in full.
Other mathematical patterns
- Deficient number
Related numbers & connections
The last two digits of a 78xx part are its output voltage, so the family is read directly from the number.
View 7812 →The 723 gave access to its internal reference and error amplifier, which the fixed three-terminal regulators that followed hid away.
View 723 →Technology & computing
The 7805 is part of the 78xx family of three-terminal positive regulators. It dissipates the excess input voltage as heat, so efficiency falls as the input-output difference grows.
DocumentedTechnology & computingPeriod: 1970s–
Common questions
Is 7805 a prime number?
No, 7805 is not prime.
What are the factors of 7805?
The factors of 7805 are 1, 5, 7, 35, 223, 1115, 1561, 7805.
About this page's data
Mathematical facts:computed directly from the number's value — nothing to source or verify externally.
Contextual records: 1 reviewer-confirmed record, sourced and reviewed before publication.
Last reviewed: 15 July 2026