The CAS Registry Mumber 679-70-9 includes 6 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 3 digits, 6,7 and 9 respectively; the second part has 2 digits, 7 and 0 respectively. Calculate Digit Verification of CAS Registry Number 679-70: (5*6)+(4*7)+(3*9)+(2*7)+(1*0)=99 99 % 10 = 9 So 679-70-9 is a valid CAS Registry Number.