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Multiplying Primes

Question

If you take all of the prime numbers under 1,000,000 and multiply them together, what digit will be in the ones place?

 

 

 

 

 

 

 

 

 

 

Answer

0. Both 2 and 5 are prime numbers (any number whose factors are only 1 and itself). Anything multiplied by 2 and 5 will have a 0 in the ones place.

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