What are the First 4 multiples of 9?

They are 9,18,27, and 36.

A general rule for finding if a number is a multiple of 9:

1: Add the digits of the number.

2: Repeat step 1 until you get a single digit.

3a: If the digit is 9, your original number is a multiple of 9.

3b: If the digit is not 9, then your original number is not a multiple of 9.

Examples:

The number is: 223243628

Add the digits: 2+2+3+2+4+3+6+2+8=32

Add the digits: 3+2=5

5≠9

223243628 is not a multiple of 9.

The number is: 27909117983733354999874

Add the digits: 2+7+9+0+9+1+1+7+9+8+3+7+3+3+3+5+4=153

Add the digits: 1+5+3=9

9=9

27909117983733354999874 is a multiple of 9