1921
1921 is the year insulin was isolated.
- Odd
- Composite
Where 1921 fits
Why 1921 is special
Diabetes went from fatal to manageable within about a year of the first human trial. The discoverers sold the patent for one dollar each, intending that nobody should profit from it — a decision whose consequences are debated in every subsequent argument about insulin pricing.
1921 is part of
Factors & digit properties
- Divisors (4)
- 1, 17, 113, 1921
- Prime factorisation
- 17 × 113
- Digit sum
- 13
- Digital root
- 4
Representations
- Decimal
- 1921
- Scientific notation
- 1.921 × 10^3
Roman numerals
M C M X X I
MCMXXI uses the subtractive pair CM: a hundred before a thousand — a thousand minus a hundred.
Binary
1 1 1 1 0 0 0 0 0 0 1
1 × 1,024 + 1 × 512 + 1 × 256 + 1 × 128 + 0 × 64 + 0 × 32 + 0 × 16 + 0 × 8 + 0 × 4 + 0 × 2 + 1 × 1 = 1,921
Octal
3 6 0 1
3 × 512 + 6 × 64 + 0 × 8 + 1 × 1 = 1,921
Hexadecimal
7 8 1
7 × 256 + 8 × 16 + 1 × 1 = 1,921
Read as powers of two: 1,024 + 512 + 256 + 128 + 1 = 1,921.
In historical numeral systems
Egyptian
1 lotus, 9 coils of rope, 2 hobbles, 1 stroke
1 × 1,000 + 9 × 100 + 2 × 10 + 1 × 1 = 1,921. The signs are simply repeated and added; where they sit on the line is a matter of layout, not value.
Babylonian
3 corner wedges + 2 vertical wedges (sixties place), 1 vertical wedge (units place)
32 × 60 + 1 = 1921. 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
- Semiprime
- Lucky number (mathematical sieve)
Related numbers & connections
1921 is a year in the 20th century, in the 1920s.
Insulin's discoverers sold the patent for a dollar in 1921 and Salk declined to patent the polio vaccine in 1955. Both decisions are cited in every modern argument about drug pricing.
View 1955 →Science
In 1921, insulin was isolated at the University of Toronto (North America).
DocumentedScienceGeography: North AmericaPeriod: 1921Insulin's discoverers transferred the patent to the University of Toronto for a nominal dollar so it could not be monopolised. That the drug is now among the most contested in pricing debates is a direct commentary on how little a patent decision constrains a market a century later.
DocumentedScienceGeography: CanadaPeriod: 1921
Common questions
Is 1921 a prime number?
No, 1921 is not prime.
What are the factors of 1921?
The factors of 1921 are 1, 17, 113, 1921.
What is 1921 in Roman numerals?
1921 in Roman numerals is MCMXXI. CM is subtractive: a hundred before a thousand — a thousand minus a hundred. Written additively it would be MDCCCCXXI, which Roman inscriptions used freely — the strict subtractive form is a later convention.
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