A number can be divided by 2, if the last digit is even: 0, 2, 4, 6, 8.
A number can be divided by 3, if its cross sum is divisible by 3.
A number can be divided by 4, if its last two digits are divisible by 4.
A number can be divided by 5, if its last digit is 0 or 5.
A number can be divided by 6, if its last digit is even AND its cross sum is divisible by 3.
A number can be divided by 8, if its last three digits are divisible by 8.
A number can be divided by 9, if its cross sum is divisible by 9.
A number can be divided by 10, if its last digit is 0.
A number can be divided by 25, if its last two digits are divisible by 25, i.e. 00, 25, 50 or 75.
A number can be divided by 100, if its last two digits are equal to 0.
A number can be divided by 1000, if its last three digits are equal to 0.
If you would like to have a vivid explanation with a detailed example, please read the page Simplifying/Reducing Fractions - Learn this magic trick!
Step 1: In what case was a number divisible by 2?
A number can be divided by 2, if the last digit is even: 0, 2, 4, 6, 8.
Step 2: Test, if the number is divisible by 2
The last digit of 15 is 5. 15 is therefore not divisible by 2.
