Let's first add up all 3 of the numbers. We get
\(781 + 691 + 3858=5330\)
Now, we have to find the prime factors of 5330. Notice that 5330 is divisble by 10. This means that 2 and 5 are factors.
\(5330/10=533\)
533 has 2 factors other than 1 and itself. The two are \(13, 41\)
This means that 5330 has 4 prime factors.
\(2, 5, 13, 41\)
Adding these up, we get
\(2+5+13+41=61\)
So 61 is our answer.
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