1556

Number
$1556$ (one thousand, five hundred and fifty-six) is:
 * $2^2 \times 389$


 * The $9$th after $4$, $13$, $38$, $87$, $208$, $377$, $666$, $1027$ in the sequence formed by adding the squares of the first $n$ primes:
 * $1556 = \ds \sum_{i \mathop = 1}^9 {p_i}^2 = 2^2 + 3^2 + 5^2 + 7^2 + 11^2 + 13^2 + 17^2 + 19^2 + 23^2$