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jmc

number theory intermediate

Problem

How many positive whole-number divisors does 196 have?
Solution
First prime factorize . The prime factorization of any divisor of 196 cannot include any primes other than 2 and 7. We are free to choose either 0, 1, or 2 as the exponent of 2 in the prime factorization of a divisor of 196. Similarly, we may choose 0, 1, or 2 as the exponent of 7. In total, there are possibilities for the prime factorization of a divisor of 196. Distinct prime factorizations correspond to distinct integers, so there are divisors of 196.
Final answer
9