Q: Is 21,390 a Prime Number?
A: No, 21,390 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 21390 can be evenly divided by 1 2 3 5 6 10 15 23 30 31 46 62 69 93 115 138 155 186 230 310 345 465 690 713 930 1,426 2,139 3,565 4,278 7,130 10,695 and 21,390, with no remainder.
Since 21,390 cannot be divided by just 1 and 21,390, it is not a prime number.