Using digits 1, 3, 5, and 7, how many 2-digit whole numbers are prime?

3,5,7 are all prime numbers. So 3 of them are prime numbers.

Ok so some two digit numbers you can make that are prime and whole are 13, 31, 51, 71, ( 11 maybe Idk if you can use one number twice to creat one number...) 53, 73, 33, 53, 55, 75, 17, 37, and 77. So the answer is 14 with the double nubers (11 33 55 77) and 10 with out. Sorry it took so long I had to get up for a sec. Hope that helped :)