521 = 20² + 11², and 521 is the hypotenuse of the primitive Pythagorean triple 279-440-521.

Print the puzzles or type the solution on this excel file: 10 Factors 2015-06-08

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- 521 is a prime number.
- Prime factorization: 521 is prime.
- The exponent of prime number 521 is 1. Adding 1 to that exponent we get (1 + 1) = 2. Therefore 521 has exactly 2 factors.
- Factors of 521: 1, 521
- Factor pairs: 521 = 1 x 521
- 521 has no square factors that allow its square root to be simplified. √521 ≈ 22.8254244

**How do we know that ****521**** is a prime number?** If 521 were not a prime number, then it would be divisible by at least one prime number less than or equal to √521 ≈ 22.8. Since 521 cannot be divided evenly by 2, 3, 5, 7, 11, 13, 17, or 19, we know that 521 is a prime number.

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