Concatinate with number format

I have numbers in two cells

5
4

and in a3 I want the answer to be 45. The lower of the two values as the first digit, with the higher of tthe two values as the second value

I've tried this formula to get the right out come =if(a2=<a1, concatenate(a2,a1), concatenate(a1,a2)) , however the problem with the formula is the A3 cell can not be summed with other cells eventhough it is formatted as number

Please advice