1. If the first digit is 1, there is only one way to factor 1 using two
integers, 1×1 = 1, so the only multiple number with 1st digit 1 is 111.
2. If the first digit is 2, there are two ways to factor 2 using two
integers, 1×2 = 2, and 2×1 = 2 so there are two multiple numbers with 1st
digit 2, 212 and 221.
3. If the first digit is 3, there are two ways to factor 3 using two
integers, 1×3 = 3, and 3×1 = 3 so there are two multiple numbers with 1st
digit 3, 313 and 331.
4. If the first digit is 4, there are three ways to factor 4 using two
integers, 1×4 = 4, 2×2 = 4 and 4×1 = 4 so there are two multiple numbers
with 1st digit 3, 414, 422 and 441.
5. If the first digit is 5, there are two ways to factor 5 using two
integers, 1×5 = 5, and 5×1 = 5 so there are two multiple numbers with 1st
digit 5, 515 and 551.
6. If the first digit is 6, there are four ways to factor 6 using two
integers, 1×6 = 6, 2×3 = 6, 3×2 = 6, and 661, so there are four multiple
numbers with 1st digit 6, 616, 623, 632, and 661.
So there are 14 of them:
111, 212, 221, 313, 331, 414, 422, 441, 515, 551, 616, 623, 632, 661
Edwin