The number 25221 is divisible by
For a number to be divisible by 2, the last digit has to be an even number.
Here, in 25221 since the last digit is 1, it is not divisible by 2.
For a number to be divisible by 9, the sum of its digits should be divisible by 9.
2+5+2+2+1 = 12.
Since 15 is not divisible by 9, 25221 is also not divisible by 9.
For a number to be divisible by 3, the sum of its digits should be divisible by 3.
2+5+2+2+1 = 12, since 12 is divisible by 3, 25221 is also divisible by 3.