Which of the following numbers is not a prime number?

The sum of four numbers is 64. If you add 3 to the first number, 3 is subtracted from second number, the third is multiplied by 3 and the sum is divided by 3, then all the results are equal. What is the difference between the largest and the smallest of the original numbers?

In a two-digit number, its units digit exceeds its tens digit by 2 and that the product of the given number and the sum of its digits is equal to 460. The number is:

The sum of the squares of two natural consecutive odd numbers is 394. The sum of the numbers is –

The digit in unit’s place of the product 81 × 82 × 83 × ... × 89 is

In a question on division, the divisor is 7 times the quotient and 3 times the remainder. If the remainder is 28, then the dividend is 

Any six-digit number that is formed by repeating a three-digit number, is always divisible by:

The sum of the two - digit number is 6 and the number and its flip (digits written in reverse order) both are multiples of 3. If the difference between them is 36, then which of the following is the required number and its flip?