"the same" vs. "equal" (about numerical quantities)

Question

Are these sentences both correct ?

"913 and 67 have the same sum of digits" vs.

"913 and 67 have equal sum of digits".

Or should it be "an equal sum of digits" ??

Note that I cannot easily move the parts of the sentence, because actually "913 and 67" can be something more articulate, like "x is the least number greater than 1 such that x and x^2 have the same sum of digits".

Thanks.

Answer 1

I think this might read better if you make sum the subject, and the actual numbers (i.e., 67 and 913) the object in a prepositional phrase:

The sums of the digits in 913 and 67 are the same.

So, going to something more articulate, we could say:

67 is the smallest number greater than 1 where the sums of the digits in x and x² are equal.