1621
1621 is the year of the first Thanksgiving harvest feast.
- Odd
- Prime
Where 1621 fits
Why 1621 is special
The event is documented in a single short letter. Almost every detail of the modern holiday — the date, the menu, the framing — was added in the nineteenth century.
Same number, different meanings
How 1621 is understood across different contexts — never implying one meaning because of another.
- Mathematics
The event is documented in a single short letter. Almost every detail of the modern holiday — the date, the menu, the framing — was added in the nineteenth century.
- History
In 1621, Robert Burton published The Anatomy of Melancholy (England).
- Culture
The 1621 harvest gathering is attested by a single brief account. The national holiday was established in 1863, and its traditions were largely constructed then rather than inherited.
1621 is part of
Factors & digit properties
- Divisors (2)
- 1, 1621
- Prime factorisation
- 1621
- Digit sum
- 10
- Digital root
- 1
Representations
- Decimal
- 1621
- Scientific notation
- 1.621 × 10^3
Roman numerals
M D C X X I
Binary
1 1 0 0 1 0 1 0 1 0 1
1 × 1,024 + 1 × 512 + 0 × 256 + 0 × 128 + 1 × 64 + 0 × 32 + 1 × 16 + 0 × 8 + 1 × 4 + 0 × 2 + 1 × 1 = 1,621
Octal
3 1 2 5
3 × 512 + 1 × 64 + 2 × 8 + 5 × 1 = 1,621
Hexadecimal
6 5 5
6 × 256 + 5 × 16 + 5 × 1 = 1,621
Read as powers of two: 1,024 + 512 + 64 + 16 + 4 + 1 = 1,621.
In historical numeral systems
Egyptian
1 lotus, 6 coils of rope, 2 hobbles, 1 stroke
1 × 1,000 + 6 × 100 + 2 × 10 + 1 × 1 = 1,621. The signs are simply repeated and added; where they sit on the line is a matter of layout, not value.
Babylonian
2 corner wedges + 7 vertical wedges (sixties place), 1 vertical wedge (units place)
27 × 60 + 1 = 1621. 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
- Twin prime
Related numbers & connections
1621 is a year in the 17th century, in the 1620s.
The Mayflower arrived in 1620 and the harvest gathering now called the first Thanksgiving followed in 1621, documented in a single short letter.
View 1620 →Numbers Around Us
- appears inHistorical years
why?
Strength 0.50, confidence "high".
Other connections
- is associated with1620
why?
Strength 0.50, confidence "high".
History
In 1621, Robert Burton published The Anatomy of Melancholy (England).
DocumentedHistoryGeography: EnglandPeriod: 1621
Culture
The 1621 harvest gathering is attested by a single brief account. The national holiday was established in 1863, and its traditions were largely constructed then rather than inherited.
DocumentedCultureGeography: MassachusettsPeriod: 1621
Common questions
Is 1621 a prime number?
Yes, 1621 is prime — it has exactly two positive divisors: 1 and itself.
What are the factors of 1621?
The factors of 1621 are 1, 1621.
What is 1621 in Roman numerals?
1621 in Roman numerals is MDCXXI.
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