9901

Number
$9901$ (nine thousand, nine hundred and one) is:


 * The $1221$st prime number


 * The $3$rd integer after $91$, $9079$ whose square has a decimal representation consisting of the concatenation of $2$ consecutive decreasing integers:
 * $9901^2 = 98 \, 029 \, 801$


 * The $6$th unique period prime after $3$, $11$, $37$, $101$, $9091$: its period is $12$:
 * $\dfrac 1 {9901} = 0 \cdotp \dot 00010 \, 09998 \, 9 \dot 9$


 * The $8$th integer after $91$, $428$, $573$, $727$, $846$, $7810$, $9079$ whose square has a decimal representation consisting of the concatenation of $2$ consecutive integers:
 * $9901^2 = 98 \, 029 \, 801$

Also see

 * Reciprocal of 9901