9801 (number)

9801 (nine thousand eight hundred [and] one) is the natural number following 9800 and preceding 9802.

In mathematics

9801 is most notable for being the third, and only 4-digit square pentagonal number, since 9801 is a square number, which can be written as: $99^2$, and it is also a pentagonal number, since it can also be written as: $\frac{81\cdot (3\cdot 81-1)}{2}=\frac{81\cdot 242}{2}$. 9801 is also the number that is below 10,000 which are integral multiples of their reversals.Template:Efn The only other number which has this property is 8712. 9801 is the sixth number such as the binomial coefficientTemplate:Efn is a perfect square.