55
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55 (number)
For other uses, see 55 (disambiguation).
| 55 | |
|---|---|
| Cardinal | fifty-five |
| Ordinal | 55th (fifty-fifth) |
| Factorization |  |
| Divisors | 1, 5, 11, 55 |
| Roman numeral | LV |
| Binary | 1101112 |
| Octal | 678 |
| Duodecimal | 4712 |
| Hexadecimal | 3716 |
55 (fifty-five) is the natural number following 54 and preceding 56.
Mathematics
Fifty-five has the interesting property that it is the 10th Fibonacci number and the sum of the numbers 1 to 10.
It is a heptagonal number, a centered nonagonal number, and a triangular number (the sum of the numbers 1 to 10) and a square pyramidal number (the sum of the squares of the integers 1 to 5). It is also a Fibonacci number (the largest Fibonacci number to also be a triangular number) and a Kaprekar number.
55 is a semiprime, being the product of 5 and 11 and it is the 2nd member of the (5.q) semiprime family. 55 is one of only two integers with an aliquot sum of 17 (the other being 39). 55 has an aliquot sequence of 4 members: (55, 17, 1, 0).
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