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30,25,15,20, or 10.
63
It is not clear what the question means: there are 31 2-digit numbers that can be expressed as a sum of two squares.
Two-digit prime numbers whose digits add up to 10 are:193773
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.