Is 243 a prime number? What are the divisors of 243?

## Parity of 243

243 is an odd number, because it is not evenly divisible by 2.

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## Is 243 a perfect square number?

A number is a perfect square (or a square number) if its square root is an integer; that is to say, it is the product of an integer with itself. Here, the square root of 243 is about 15.588.

Thus, the square root of 243 is not an integer, and therefore 243 is not a square number.

## What is the square number of 243?

The square of a number (here 243) is the result of the product of this number (243) by itself (i.e., 243 × 243); the square of 243 is sometimes called "raising 243 to the power 2", or "243 squared".

The square of 243 is 59 049 because 243 × 243 = 2432 = 59 049.

As a consequence, 243 is the square root of 59 049.

## Number of digits of 243

243 is a number with 3 digits.

## What are the multiples of 243?

The multiples of 243 are all integers evenly divisible by 243, that is all numbers such that the remainder of the division by 243 is zero. There are infinitely many multiples of 243. The smallest multiples of 243 are:

• 0: indeed, 0 is divisible by any natural number, and it is thus a multiple of 243 too, since 0 × 243 = 0
• 243: indeed, 243 is a multiple of itself, since 243 is evenly divisible by 243 (we have 243 / 243 = 1, so the remainder of this division is indeed zero)
• 486: indeed, 486 = 243 × 2
• 729: indeed, 729 = 243 × 3
• 972: indeed, 972 = 243 × 4
• 1 215: indeed, 1 215 = 243 × 5
• etc.

## How to determine whether an integer is a prime number?

To determine the primality of a number, several algorithms can be used. The most naive technique is to test all divisors strictly smaller to the number of which we want to determine the primality (here 243). First, we can eliminate all even numbers greater than 2 (and hence 4, 6, 8…). Then, we can stop this check when we reach the square root of the number of which we want to determine the primality (here the square root is about 15.588). Historically, the sieve of Eratosthenes (dating from the Greek mathematics) implements this technique in a relatively efficient manner.

More modern techniques include the sieve of Atkin, probabilistic algorithms, and the cyclotomic AKS test.

## Numbers near 243

• Preceding numbers: …241, 242
• Following numbers: 244, 245

### Nearest numbers from 243

• Preceding prime number: 241
• Following prime number: 251
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