The CAS Registry Mumber 89438-15-3 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 8,9,4,3 and 8 respectively; the second part has 2 digits, 1 and 5 respectively. Calculate Digit Verification of CAS Registry Number 89438-15: (7*8)+(6*9)+(5*4)+(4*3)+(3*8)+(2*1)+(1*5)=173 173 % 10 = 3 So 89438-15-3 is a valid CAS Registry Number.