1225
1,225 is both a perfect square and a triangular number.
Where 1225 fits
Why 1225 is special
It is 35 squared and the sum of the numbers from 1 to 49. Numbers that are both are rare and thin out quickly — 1, 36, 1225, 41616 — and they satisfy a Pell equation, which is why they can be generated rather than searched for.
1225 is part of
Factors & digit properties
- Divisors (9)
- 1, 5, 7, 25, 35, 49, 175, 245, 1225
- Prime factorisation
- 5^2 × 7^2
- Digit sum
- 10
- Digital root
- 1
Representations
- Decimal
- 1225
- Scientific notation
- 1.225 × 10^3
Roman numerals
M C C X X V
Binary
1 0 0 1 1 0 0 1 0 0 1
1 × 1,024 + 0 × 512 + 0 × 256 + 1 × 128 + 1 × 64 + 0 × 32 + 0 × 16 + 1 × 8 + 0 × 4 + 0 × 2 + 1 × 1 = 1,225
Octal
2 3 1 1
2 × 512 + 3 × 64 + 1 × 8 + 1 × 1 = 1,225
Hexadecimal
4 c 9
4 × 256 + c × 16 + 9 × 1 = 1,225
Read as powers of two: 1,024 + 128 + 64 + 8 + 1 = 1,225.
In historical numeral systems
Egyptian
1 lotus, 2 coils of rope, 2 hobbles, 5 strokes
1 × 1,000 + 2 × 100 + 2 × 10 + 5 × 1 = 1,225. 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 + 5 vertical wedges (units place)
20 × 60 + 25 = 1225. 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
- Triangular number
- Deficient number
- Powerful number
- Hexagonal number
Related numbers & connections
1225 is a year in the 13th century, in the 1220s.
Both are square and triangular at once. The sequence runs 1, 36, 1225, 41616 and thins so fast that the fourth term is already beyond most catalogues.
View 36 →History
In 1225, Thomas Aquinas was born near Aquino (Italy).
DocumentedHistoryGeography: ItalyPeriod: 1225
Mathematics
1,225 is 35 squared and also 1 + 2 + … + 49. Square triangular numbers are scarce and follow a generating rule from Pell's equation, so the sequence can be produced directly rather than found by testing.
DocumentedMathematics
Common questions
Is 1225 a prime number?
No, 1225 is not prime.
What are the factors of 1225?
The factors of 1225 are 1, 5, 7, 25, 35, 49, 175, 245, 1225.
What is 1225 in Roman numerals?
1225 in Roman numerals is MCCXXV.
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