The CAS Registry Mumber 76531-98-1 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 7,6,5,3 and 1 respectively; the second part has 2 digits, 9 and 8 respectively. Calculate Digit Verification of CAS Registry Number 76531-98: (7*7)+(6*6)+(5*5)+(4*3)+(3*1)+(2*9)+(1*8)=151 151 % 10 = 1 So 76531-98-1 is a valid CAS Registry Number.