There are four 2-digit prime numbers that have 4 as one of their digits: 41, 43, 47, and 49. However, 49 is not a Prime number because it is divisible by 7. So, the correct answer is three 2-digit prime numbers with 4 as one of their digits.
There are 5460 five digit numbers with a digit sum of 22.
There is no simple formula for that; I suggest you look up the prime numbers in a table of prime numbers, analyzing each prime number in the range 10-99 whether it fulfills this specific criterion.
There are 60480 numbers.
To find the even two-digit numbers where the sum of the digits is 5, we need to consider the possible combinations of digits. The digits that sum up to 5 are (1,4) and (2,3). For the numbers to be even, the units digit must be 4, so the possible numbers are 14 and 34. Therefore, there are 2 even two-digit numbers where the sum of the digits is 5.
There are 5760 such numbers.
there are 4
61 42 56 89
There are 21 two-digit prime numbers.
With 123 digits you can make 123 one-digit numbers.
There are 5460 five digit numbers with a digit sum of 22.
3 41 43 47
27 three digit numbers from the digits 3, 5, 7 including repetitions.
There is no simple formula for that; I suggest you look up the prime numbers in a table of prime numbers, analyzing each prime number in the range 10-99 whether it fulfills this specific criterion.
There are 7,290 different 4-digit numbers that can be formed from the digits 1-9 without repetition.
There are 17 such numbers.
7 two-digit numbers.
There are 9 digits that can be the first digit (1-9); for each of these there is 1 digit that can be the second digit (6); for each of these there are 10 digits that can be the third digit (0-9); for each of these there are 10 digits that can be the fourth digit (0-9). → number of numbers is 9 × 1 × 10 × 10 = 900 such numbers.