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1. 2 numbers (9 and 37)
2. None, if it is divisible by 4 then when divided by 8 there has to be a remainder of 4 or 0.
3. a remainder of 2
4. No prime can be written as the sum of two composite numbers because one is not prime or composite and every composite number is even. Prime numbers are odd and two evens do not make an odd.
Only five number under 50 can be written as the sum of two primes (5, 13, 19, 31, 43). 2 has to be added to that number because two odds make an even.. non prime. If two has to be added, the prime number before the answer has to be 2 lower than it. There are only five such numbers (shown above).