The first digit can be any one of 9 digits (anything but zero). For each of those ...
The second digit can be any one of 9 digits (anything but the previous one). For each of those ...
The third digit can be any one of 9 digits (anything but the previous one). For each of those ...
The fourth digit can be any one of 9 digits (anything but the previous one). For each of those ...
The fifth digit can be any one of 9 digits (anything but the previous one).
So the total number of possible arrangements is (9 x 9 x 9 x 9 x 9) = 59,049
out of a total of 99,999 different 5-digit numbers, or 59.05%.
89 x 90 = 8010 which are two consecutive two digit numbers that equal 8010.
24
There are only two prime numbers that are consecutive numbers, 2 and 3. Their product is 2 x 3 = 6. The first prime numbers are 2, 3, 5, and 7 and the only two consecutive prime numbers whose product is a single digit are 2 and 3. (The next two consecutive prime numbers, 3 and 5, have a two-digit product.)
1
121
89 x 90 = 8010 which are two consecutive two digit numbers that equal 8010.
Any 2 consecutive will always add up to an odd number and the number given is an even number
89
24
There are only two prime numbers that are consecutive numbers, 2 and 3. Their product is 2 x 3 = 6. The first prime numbers are 2, 3, 5, and 7 and the only two consecutive prime numbers whose product is a single digit are 2 and 3. (The next two consecutive prime numbers, 3 and 5, have a two-digit product.)
1
121
21 and 20
no
The 2-digit number must be 20, because it is the only 2-digit number whose sum of its two even digits, 2 + 0 = 2, is greater than the product of its two even digits, 2 x 0 = 0. Moreover, 20 is a product of the two consecutive integers 4 and 5.
No. When adding the smallest 2 digit number (= 10) to the smallest 2 digit number (again, 10) the result is a 2 digit number (10 + 10 = 20). When adding the largest 2 digit number (= 99) to the largest 2 digit number (again, 99) the result is a 3 digit number (99 + 99 = 198). As you can see, you'll either get a 2 or 3 digit number, but never a 4 digit number.
The number 64 is equal to ±8 squared and 4 cubed.