1821
1821 is the year Faraday demonstrated electromagnetic rotation.
- Odd
- Composite
Where 1821 fits
Why 1821 is special
A wire carrying current rotated around a magnet — the first conversion of electrical energy into continuous mechanical motion, and the ancestor of every electric motor.
1821 is part of
Factors & digit properties
- Divisors (4)
- 1, 3, 607, 1821
- Prime factorisation
- 3 × 607
- Digit sum
- 12
- Digital root
- 3
Representations
- Decimal
- 1821
- Scientific notation
- 1.821 × 10^3
Roman numerals
M D C C C X X I
Binary
1 1 1 0 0 0 1 1 1 0 1
1 × 1,024 + 1 × 512 + 1 × 256 + 0 × 128 + 0 × 64 + 0 × 32 + 1 × 16 + 1 × 8 + 1 × 4 + 0 × 2 + 1 × 1 = 1,821
Octal
3 4 3 5
3 × 512 + 4 × 64 + 3 × 8 + 5 × 1 = 1,821
Hexadecimal
7 1 d
7 × 256 + 1 × 16 + d × 1 = 1,821
Read as powers of two: 1,024 + 512 + 256 + 16 + 8 + 4 + 1 = 1,821.
In historical numeral systems
Egyptian
1 lotus, 8 coils of rope, 2 hobbles, 1 stroke
1 × 1,000 + 8 × 100 + 2 × 10 + 1 × 1 = 1,821. The signs are simply repeated and added; where they sit on the line is a matter of layout, not value.
Babylonian
3 corner wedges (sixties place), 2 corner wedges + 1 vertical wedge (units place)
30 × 60 + 21 = 1821. Places are separated by a space on the tablet, with the higher place written first.
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
- Happy number
- Semiprime
Related numbers & connections
1821 is a year in the 19th century, in the 1820s.
Volta's pile of 1800 gave steady current and Faraday's 1821 apparatus turned current into continuous motion. Every electric motor descends from that pair.
View 1800 →Numbers Around Us
- appears inHistorical years
why?
Strength 0.50, confidence "high".
Other connections
- developed from1800
why?
Strength 0.50, confidence "high".
Technology & computing
In 1821, Michael Faraday demonstrated electromagnetic rotation, the principle of the electric motor (England).
DocumentedTechnology & computingGeography: EnglandPeriod: 1821Faraday's 1821 apparatus turned electrical energy into continuous rotation for the first time. Every electric motor, from a fan to a train, is a development of that demonstration.
DocumentedTechnology & computingGeography: EnglandPeriod: 1821
Common questions
Is 1821 a prime number?
No, 1821 is not prime.
What are the factors of 1821?
The factors of 1821 are 1, 3, 607, 1821.
What is 1821 in Roman numerals?
1821 in Roman numerals is MDCCCXXI.
About this page's data
Mathematical facts:computed directly from the number's value — nothing to source or verify externally.
Contextual records: 2 reviewer-confirmed records, sourced and reviewed before publication.
Last reviewed: 15 July 2026