256

Number
$256$ (two hundred and fifty-six) is:


 * $2^8$


 * The $4$th fourth power after $1, 16, 81$:
 * $256 = 4 \times 4 \times 4 \times 4$


 * The $9$th almost perfect number after $1, 2, 4, 8, 16, 32, 64, 128$:
 * $\sigma \left({256}\right) = 511 = 2 \times 256 - 1$