It is possible to find out using mathematical methods whether a given integer is a prime number or not.
No, 129 991 is not a prime number.
For example, 129 991 can be divided by 61: 129 991 / 61 = 2 131.
For 129 991 to be a prime number, it would have been required that 129 991 has only two divisors, i.e., itself and 1.
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129 991 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 129 991 is about 360.543.
Thus, the square root of 129 991 is not an integer, and therefore 129 991 is not a square number.
The square of a number (here 129 991) is the result of the product of this number (129 991) by itself (i.e., 129 991 × 129 991); the square of 129 991 is sometimes called "raising 129 991 to the power 2", or "129 991 squared".
The square of 129 991 is 16 897 660 081 because 129 991 × 129 991 = 129 9912 = 16 897 660 081.
As a consequence, 129 991 is the square root of 16 897 660 081.
The multiples of 129 991 are all integers evenly divisible by 129 991, that is all numbers such that the remainder of the division by 129 991 is zero. There are infinitely many multiples of 129 991. The smallest multiples of 129 991 are: