55 (number) facts for kids
Fifty-five is a number that comes right after fifty-four and before fifty-six. It's an odd number, which means you can't divide it evenly by 2. You can divide 55 by 1, 5, 11, and 55 itself without getting a remainder. These numbers are called its factors.
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Fun Facts About 55
Fifty-five is a really interesting number with some cool mathematical properties!
A Triangular Number
Imagine arranging dots to form triangles. A triangular number is the total number of dots in a triangle where each side has the same number of dots. Fifty-five is the 10th triangular number. This means if you add up all the numbers from 1 to 10 (1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 10), you get 55!
A Fibonacci Number
Fifty-five is also part of the famous Fibonacci sequence. This sequence starts with 0 and 1, and each new number is found by adding the two numbers before it (0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55...). Fifty-five is the 10th number in this sequence (if you start counting from 0 as the 0th number).
A Pentagonal Number
Just like triangular numbers, pentagonal numbers are numbers that can form a regular five-sided shape (a pentagon). Fifty-five is the 5th pentagonal number.
A Semiprime Number
A semiprime number is a number that is the result of multiplying exactly two prime numbers together. Fifty-five is a semiprime because it's 5 multiplied by 11 (5 × 11 = 55), and both 5 and 11 are prime numbers.
A Kaprekar Number
A Kaprekar number is a positive integer that, when squared, can be split into two parts (which can be different lengths) that add up to the original number. For 55:
- 55 squared (55 × 55) is 3025.
- If you split 3025 into 30 and 25, and then add them together (30 + 25), you get 55!
Where We See 55
The number 55 appears in many different places around us.
In Science
- In chemistry, Caesium (often spelled Cesium) is a chemical element with the atomic number 55. It's a soft, silvery-gold metal that is very reactive.
In Sports
- Many athletes wear the number 55 on their jerseys in sports like basketball, football, and hockey. For example, famous basketball player Dikembe Mutombo wore number 55.
In Everyday Life
- In some countries, 55 used to be a common speed limit in miles per hour (mph) on highways.
- You might see 55 in addresses, phone numbers, or other everyday counts.
