Math Olympiad for 3rd Grade – 4

Kevin was calculating the product of two numbers. One of the numbers is 78. However, instead of using 78, he was using 87 and the result was off by 45. The other number used in multiplication is __________.
The sum of two 3-digit numbers, $abc$ and $def$, is 1995. Then the sum of all 6 digits $a+b+c+d+e+f$ is __________.
The difference of two 3-digit numbers, $abc$ and $def$, is 892. Then the products of all digits of two numbers, $a\times b\times c\times c\times d\times e\times f$ is __________.
Comparing $345\times 347$ to $346 \times 346$, which one is bigger? __________.
The sum of several natural numbers is $11$. The maximum possible value of multiple them together is __________.