81
Number 81 properties
- 81 is an odd number.
- 81 is a perfect square (9 × 9).
- 81 is a Harshad number, which means it is divisible by the sum of its digits (81 = 9, and 81 is divisible by 9).
Number 81 - properties and curiosities
81 (number)
Prime factorization
Prime factorization of 81: 3^4.
Divisors
Divisor count: 5
1, 3, 9, 27, 81
Factors of 81 are: 1, 3, 9, 27, 81.
Representations
In octal, 81 is represented as 121.
In binary, 81 is represented as 1010001.
In hex, 81 is represented as 51.
Roman numeral: LXXXI
Curiosities
- 81 is a perfect square, so it forms a square grid with equal side lengths.
- 81 is divisible by the sum of its digits.
Related numbers
Quick answers
Is 81 prime?
No, 81 is not prime.
What are the factors of 81?
1, 3, 9, 27, 81
What is 81 in binary?
1010001