Which of the following describes 81 accurately?
81 is a prime number
81 is a composite number
81 is a perfect square
81 is a rational number
Why No: 81 is not a prime number because it does not meet the prime criteria of having exactly two distinct positive divisors: 1 and itself. See Prime number checker
Why Yes: 81 is a composite number because it has more than two distinct positive divisors. It is divisible by 1, 3, 9, 27, and itself (81).
Property | Answer |
---|---|
Is 81 a prime number? | No |
Is 81 a composite number? | Yes |
Is 81 a perfect square? | Yes |
Factors of 81 | 1, 3, 9, 27, 81 |
Multiples of 81 | 81, 162, 243, 324, 405, 486, 567, 648, 729, 810 |
Cube Root of 81 | 4.327 |
Square of 81 | 6561 |
Square Root of 81 | 9 |
Is 81 a Perfect Cube? | No |
Is 81 an Irrational number | No |
Is 81 a Rational number | Yes |
Is 81 a Real number | Yes |
Is 81 an Integer | Yes |
Is 81 a Natural number | Yes |
Is 81 a Whole number | Yes |
Is 81 an Even or odd number | Yes (81 is an odd number) |
Is 81 an Ordinal number | Yes |
Is 81 a Complex number | Yes (as all real numbers are also complex numbers) |
The factors of 81 are 1, 3, 9, 27, and 81. 81 is not a prime number because it is divisible by numbers other than 1 and itself, demonstrating it has more than two factors. This clarity confirms that it is a composite number, not a prime number.
The nearest prime numbers to 81 are 79 and 83. 79 is the closest prime number less than 81, and 83 is the closest prime number greater than 81.
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Which of the following describes 81 accurately?
81 is a prime number
81 is a composite number
81 is a perfect square
81 is a rational number
What can be said about the number 81 if it can be divided evenly by 3?
It is a prime number
It is a composite number
It is a fraction
It is an irrational number
Which of these is not a factor of 81?
1
9
12
27
Which of these statements is true about 81?
81 is a perfect square
81 is a prime number
81 is a prime factor
81 is a fraction
What type of number is 81 if it is divisible by both 9 and 27?
Prime
Composite
Real
Imaginary
What property confirms that 81 is not a prime number?
It is divisible by 3
It ends in 1
It is an odd number
It is greater than 50
Which of the following statements is true for 81?
It is a prime number
It can be expressed as 9 × 9
It is less than 100
It is divisible by 2
Which of these is a property of composite numbers like 81?
They are divisible by more than two numbers
They are only divisible by 1 and themselves
They are always even
They are always prime
What type of number is 81 if it is divisible by 3 and 9?
Prime
Composite
Rational
Whole
Which statement is accurate for the number 81?
It has exactly two factors
It is a prime number
It is a composite number with multiple factors
It cannot be divided by 1
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