Sums of Two Squares – Math Fun Facts
math.hmc.edu › funfacts › sums-of-two-squaresA number N is expressible as a sum of 2 squares if and only if in the prime factorization of N, every prime of the form (4k+3) occurs an even number of times! Examples: 245 = 5*7*7. The only prime of the form 4k+3 is 7, and it appears twice. So it should be possible to write 245 as a sum of 2 squares (in fact, try the squares of 14 and 7).
Which Numbers are the Sum of Two Squares?
www.wstein.org › edu › 124Theorem 1.1 A number is a sum of two squares if and only if all prime factors of of the form have even exponent in the prime factorization of . Before tackling a proof, we consider a few examples. Example 1.2. . is not a sum of two squares. is divisible by because is, but not by since is not, so is not a sum of two squares.