# Is 21510 a prime number?

It is possible to find out using mathematical methods whether a given integer is a prime number or not.

No, 21 510 is not a prime number.

For example, 21 510 can be divided by 2: 21 510 / 2 = 10 755.

Actually, one can immediately see that 21 510 cannot be prime, because 5 is one of its divisors: indeed, a number ending with 0 or 5 has necessarily 5 among its divisors.
The last digit of 21 510 is 0, so it is divisible by 5 and is therefore *not* prime.

For 21 510 to be a prime number, it would have been required that 21 510 has only two divisors, i.e., itself and 1.

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