The CAS Registry Mumber 6979-72-2 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 6,9,7 and 9 respectively; the second part has 2 digits, 7 and 2 respectively. Calculate Digit Verification of CAS Registry Number 6979-72: (6*6)+(5*9)+(4*7)+(3*9)+(2*7)+(1*2)=152 152 % 10 = 2 So 6979-72-2 is a valid CAS Registry Number.