Numberwise

1221

1221 Amor gave its name to a whole orbital class.

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Where 1221 fits

Where 1221 fits: Mathematics, History, Related numbersMathematics: Palindromic number, Happy number. History: Historical years. Related numbers: 887, 2101, 1036.MathematicsPalindromic numberHappy numberHistoryHistorical yearsRelated numbers887210110361221
1221 connects to 3 worlds: mathematics, history, related numbers.

Why 1221 is special

Asteroids that approach Earth's orbit without crossing it are called Amors after this one, which is how an individual object becomes a category.

1221 connects to:

  • historical years — appears in
  • 887 — is associated with
  • 2101 — is associated with
  • 1036 — is associated with

Same number, different meanings

How 1221 is understood across different contexts — never implying one meaning because of another.

1221 is part of

Happy numbersRepeating / palindromic numbersNumbers around us

Factors & digit properties

Divisors (8)
1, 3, 11, 33, 37, 111, 407, 1221
Prime factorisation
3 × 11 × 37
Digit sum
6
Digital root
6

Representations

Decimal
1221
Scientific notation
1.221 × 10^3

Roman numerals

M C C X X I

Binary

1 0 0 1 1 0 0 0 1 0 1

1 × 1,024 + 0 × 512 + 0 × 256 + 1 × 128 + 1 × 64 + 0 × 32 + 0 × 16 + 0 × 8 + 1 × 4 + 0 × 2 + 1 × 1 = 1,221

Octal

2 3 0 5

2 × 512 + 3 × 64 + 0 × 8 + 5 × 1 = 1,221

Hexadecimal

4 c 5

4 × 256 + c × 16 + 5 × 1 = 1,221

Read as powers of two: 1,024 + 128 + 64 + 4 + 1 = 1,221.

In historical numeral systems

Egyptian

1 lotus, 2 coils of rope, 2 hobbles, 1 stroke

1 × 1,000 + 2 × 100 + 2 × 10 + 1 × 1 = 1,221. The signs are simply repeated and added; where they sit on the line is a matter of layout, not value.

Babylonian

2 corner wedges (sixties place), 2 corner wedges + 1 vertical wedge (units place)

20 × 60 + 21 = 1221. 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

Related numbers & connections

Documented appearance
1221 is a year in the 13th century, in the 1220s.

1221 is a year in the 13th century, in the 1220s.

Connection
Resonance with Jupiter steadily raises eccentricity, which is one way objects arrive on Earth-crossing orbits.

Resonance with Jupiter steadily raises eccentricity, which is one way objects arrive on Earth-crossing orbits.

View 887 →

Numbers Around Us

  • appears inHistorical years
    why?

    Strength 0.50, confidence "high".

Other connections

  • is associated with887
    why?

    Strength 0.50, confidence "high".

  • is associated with2101
    why?

    Strength 0.50, confidence "high".

  • is associated with1036
    why?

    Strength 0.50, confidence "high".

How is 1221 connected to another number? →

History

  • In 1221, the Dominicans held their first general chapter, organising the order for study and preaching (Europe).

    DocumentedHistoryGeography: EuropePeriod: 1221

Science

  • 1221 Amor is the namesake of the Amor group, near-Earth asteroids with perihelia outside Earth's orbit but within 1.3 astronomical units of the Sun.

    DocumentedSciencePeriod: 1932–

Common questions

Is 1221 a prime number?

No, 1221 is not prime.

What are the factors of 1221?

The factors of 1221 are 1, 3, 11, 33, 37, 111, 407, 1221.

What is 1221 in Roman numerals?

1221 in Roman numerals is MCCXXI.

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