It is possible to find out using mathematical methods whether a given integer is a prime number or not.
No, 8 421 is not a prime number.
For example, 8 421 can be divided by 3: 8 421 / 3 = 2 807.
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For 8 421 to be a prime number, it would have been required that 8 421 has only two divisors, i.e., itself and 1.
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8 421 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 8 421 is about 91.766.
Thus, the square root of 8 421 is not an integer, and therefore 8 421 is not a square number.
The square of a number (here 8 421) is the result of the product of this number (8 421) by itself (i.e., 8 421 × 8 421); the square of 8 421 is sometimes called "raising 8 421 to the power 2", or "8 421 squared".
The square of 8 421 is 70 913 241 because 8 421 × 8 421 = 8 4212 = 70 913 241.
As a consequence, 8 421 is the square root of 70 913 241.
The multiples of 8 421 are all integers evenly divisible by 8 421, that is all numbers such that the remainder of the division by 8 421 is zero. There are infinitely many multiples of 8 421. The smallest multiples of 8 421 are: