Playing with Nu...

Which of the following numbers are co-prime?
a) $$18$$ and $$35$$ 
b) $$15$$ and $$37$$ 
c) $$30$$ and $$415$$
d) $$17$$ and $$68$$
e) $$216$$ and $$215$$
f) $$81$$ and $$16$$

How many two-digit prime numbers are there having the digit $$3$$ in their units place?

Which of the following number is divisible by $$6$$?

The factor of 252 is:

Which of the following is divisible by $$9$$?

The sum of prime numbers, out of the numbers $$17, 8, 21, 13, 41, 2, 27, 31, 51$$ is:

Which of the following is a prime number?

Which of the following is a prime number?

If the sum of digits of a number is divisible by three then the number is always divisible by