Number 81
The number 81 is a perfect square (9²). It has 5 divisors and a digital root of 9. Explore its full properties below, or find words and phrases with a gematria value of 81.
81
Divisors: 5
1, 3, 9, 27, 81
Sum: 121
Prev Square: 64
9th Square Number
Next Square: 100
Mathematical Properties
Golden Numbern/a
Reduced Digit Sum9
Magic Constant265,761
Digital Root9
Octaln/a(121)
Duodecimal97(69)
Hexadecimal129(51)
Binary1010001
81st Values
Prime419
Triangular3,321
Square6,561
Star38,881
Pentagonal9,801
Cube531,441
Tetrahedral91,881
Square Pyramidal180,441
Fibonaccin/a
Harshad280
Happy Number637