Q: Is 21,820 a Prime Number?
A: No, 21,820 is not a prime number.
A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 21820 can be evenly divided by 1 2 4 5 10 20 1,091 2,182 4,364 5,455 10,910 and 21,820, with no remainder.
Since 21,820 cannot be divided by just 1 and 21,820, it is not a prime number.