How to add up first digits to all the prime numbers within a given range ?

In MATLAB, primes(N) provides all the prime numbers less than or equal to N. E.g. primes(15) = [2 3 5 7 11 13]. The sum of the first digit of each prime is 19 (i.e. 2+3+5+7+1+1 = 19).

What is the sum of the first digit of all primes less than or equal to 77777? You may want to use the num2str() function.

Answer 1

[Image Analyst]

Here's a start

p = primes(77777)
theSum = 0;
for k = 1 : length(p)
	str = num2str(............
	theSum = theSum + double(................
end

You finish it, since you're not allowed to turn in my code as your own. If you need more help, read this:

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