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.
1621 is part of
Factors & digit properties
- Divisors (2)
- 1, 1621
- Prime factorisation
- 1621
- Digit sum
- 10
- Digital root
- 1
Representations
- Decimal
- 1621
- Binary
- 11001010101
- Octal
- 3125
- Hexadecimal
- 655
- Roman numeral
- MDCXXI
- Scientific notation
- 1.621 × 10^3
Other mathematical patterns
- Deficient number
- Twin prime
Related numbers & connections
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 →Other connections
- is associated with1620
why?
Strength 0.50, confidence "high".
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: 1 reviewer-confirmed record, sourced and reviewed before publication.
Last reviewed: 3 August 2026