Data update

Task/Additive-primes/Fortran/additive-primes.f

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+program AdditivePrimes
+      implicit none
+
+      integer :: i, j, digit_sum, count
+      logical :: is_prime
+
+      ! Arrays to track prime numbers and additive primes
+      logical, dimension(500) :: prime_check
+      logical, dimension(500) :: additive_prime_check
+
+      ! Initialize arrays
+      prime_check = .true.
+      prime_check(1) = .false.
+      additive_prime_check = .false.
+
+      ! Sieve of Eratosthenes to find primes
+      do i = 2, int(sqrt(real(500)))
+        if (prime_check(i)) then
+          do j = i*i, 500, i
+            prime_check(j) = .false.
+          end do
+        end if
+      end do
+
+      ! Find additive primes
+      count = 0
+      do i = 2, 500
+        if (prime_check(i)) then
+          ! Calculate digit sum
+          digit_sum = sum_digits(i)
+
+          ! Check if digit sum is also prime
+          if (prime_check(digit_sum)) then
+            additive_prime_check(i) = .true.
+            count = count + 1
+          end if
+        end if
+      end do
+
+      ! Print results
+      print *, "Additive Primes less than 500:"
+      do i = 2, 500
+        if (additive_prime_check(i)) then
+          print *, i
+        end if
+      end do
+
+      print *, "Total number of additive primes:", count
+
+      contains
+
+      ! Function to calculate sum of digits
+      function sum_digits(num) result(total)
+        integer, intent(in) :: num
+        integer :: total, temp_num
+
+        total = 0
+        temp_num = num
+
+        do while (temp_num > 0)
+          total = total + mod(temp_num, 10)
+          temp_num = temp_num / 10
+        end do
+      end function sum_digits
+
+      end program AdditivePrimes