Numerosidad Number Atlas
The number 55, visualized
Fifty-five has a particularly balanced Numerosidad form: five triangle-shaped tens beside five circle-shaped ones.
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Fixed-value symbol model for 55
five tens + five ones
Five triangle-shaped fixed-value symbols worth 10 each represent 50, and five circle-shaped fixed-value symbols worth 1 each represent 5.
This additive decimal model decomposes the number into repeated fixed-value symbols. Each symbol keeps its value wherever it appears, and repetitions add, so the complete pattern composes 55.
- five tens
- 50
- five ones
- 5
Number profile
Facts about 55
- Standard form
- 55
- Number name (word form)
- fifty-five
- Expanded form
- 50 + 5
- Classification
- Odd and composite
- Prime factorization
- 5 × 11
- Positive divisors (4)
- 1, 5, 11, 55
- Digits
- 2
- Digit sum
- 10
- Digital root
- 1
- Fixed-value symbols
- 10
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Why it stands out
Patterns inside 55
Fifty-five connects Fibonacci growth, triangular sums, a two-digit palindrome, and the compact prime factorization 5 × 11.
Two sequence milestones meet at 55
The number 55 is F(10) when F(0) = 0 and F(1) = 1, and it is also the 10th triangular number.
Its prime factorization is 5 × 11
That factorization gives 55 four positive divisors: 1, 5, 11, and 55.
Its repeated digits make a palindrome
The two digits are identical, so reversing their order leaves the number unchanged.