625

Number
$625$ (six hundred and twenty-five) is:


 * $5^4$


 * The $25$th square number after $1, 4, 9, 16, 25, 36, \ldots, 361, 400, 441, 484, 529, 576$:
 * $625 = 25 \times 25$


 * The $5$th fourth power after $1, 16, 81, 256$:
 * $625 = 5 \times 5 \times 5 \times 5$


 * The $7$th automorphic number after $1, 5, 6, 25, 76, 376$:
 * $625^2 = 390 \, \mathbf {625}$


 * The $21$st positive integer which cannot be expressed as the sum of a square and a prime:
 * $1, 10, 25, 34, 58, 64, 85, 91, 121, 130, 169, 196, 214, 226, 289, 324, 370, 400, 526, 529, 625, \ldots$