26207

My solution

If you add three consecutive numbers together for example 1,2,3 they equal 6 2x3=6. Eg 89,90,91 they equal 270 which is a multiple of 3. Lets try bigger numbers eg. 351,352,353 they equal 1056.3 goes into 1056 352 times. That shows that three consecutive numbers always add up to a multiple of three no matter how big they are but they have to be consecutive numbers for this solution to work.