It is possible to find out using mathematical methods whether a given integer is a prime number or not.
No, 20 009 is not a prime number.
For example, 20 009 can be divided by 11: 20 009 / 11 = 1 819.
For 20 009 to be a prime number, it would have been required that 20 009 has only two divisors, i.e., itself and 1.
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20 009 is an odd number, because it is not evenly divisible by 2.
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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 20 009 is about 141.453.
Thus, the square root of 20 009 is not an integer, and therefore 20 009 is not a square number.
The square of a number (here 20 009) is the result of the product of this number (20 009) by itself (i.e., 20 009 × 20 009); the square of 20 009 is sometimes called "raising 20 009 to the power 2", or "20 009 squared".
The square of 20 009 is 400 360 081 because 20 009 × 20 009 = 20 0092 = 400 360 081.
As a consequence, 20 009 is the square root of 400 360 081.
The multiples of 20 009 are all integers evenly divisible by 20 009, that is all numbers such that the remainder of the division by 20 009 is zero. There are infinitely many multiples of 20 009. The smallest multiples of 20 009 are: