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A1. Integers
Prime factor decomposition

Vocabulary Both 2 and 3 are factors of 12; 2 and 3 are also prime numbers. Therefore, we say that 2 and 3 are prime factors of 12. They are the only prime factors of 12. When 12 is written as 2 × 2 × 3, it has been written as a product of its prime factors. The number 15 can be written as 3 × 5 The number 18 can be written as 2 × 3 × 3. The number 28 can be written as 2 × 2 × 7. The process of expressing a number as a product of its prime factors is called prime factor decomposition. Often the product of prime factors is written using index notation, for example, 18=2 × 3², 28=2² × 7. Can you find any decompositions where each prime factor occurs twice? Enter a number:

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