SUMPRODUCT(...)

Category: Math and trigonometry

Returns the sum of the products of corresponding array components

SUMPRODUCT(array1, [array2], [array3], ...)

Category: Math and trigonometry

Returns the remainder from division

MOD(number, divisor)

Category: Lookup and reference

Returns the row number of a reference

ROW([reference])

Category: Lookup and reference

Returns a reference indicated by a text value

INDIRECT(ref_text, [a1])

0

This formula checks if a number is perfectly divisible by any other number for this case it is 3, by checking the remainder of the division. If the remainder is zero then it counts all such numbers to give the final answer.