The CAS Registry Mumber 67977-04-2 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 6,7,9,7 and 7 respectively; the second part has 2 digits, 0 and 4 respectively. Calculate Digit Verification of CAS Registry Number 67977-04: (7*6)+(6*7)+(5*9)+(4*7)+(3*7)+(2*0)+(1*4)=182 182 % 10 = 2 So 67977-04-2 is a valid CAS Registry Number.