325

Number
$325$ (three hundred and twenty-five) is:


 * $5^2 \times 13$


 * The $25$th triangular number after $1, 3, 6, 10, 15, \ldots, 171, 190, 210, 231, 253, 276, 300$:
 * $325 = \displaystyle \sum_{k \mathop = 1}^{25} k = \dfrac {25 \times \left({25 + 1}\right)} 2$


 * The $13$th hexagonal number after $1, 6, 15, 28, 45, 66, 91, 120, 153, 190, 231, 276$:
 * $325 = \displaystyle \sum_{k \mathop = 1}^{13} \left({4 k - 3}\right) = 13 \left({2 \times 13 - 1}\right)$


 * The $10$th positive integer after $200, 202, 204, 205, 206, 208, 320, 322, 324$ that cannot be made into a prime number by changing just $1$ digit


 * The smallest positive integer which can be expressed as the sum of two square numbers in two distinct ways:
 * $325 = 18^2 + 1^2 = 17^2 + 6^2 = 15^2 + 10^2$

Also see

 * Sum of 2 Squares in 3 Distinct Ways