The CAS Registry Mumber 6427-30-1 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 6,4,2 and 7 respectively; the second part has 2 digits, 3 and 0 respectively. Calculate Digit Verification of CAS Registry Number 6427-30: (6*6)+(5*4)+(4*2)+(3*7)+(2*3)+(1*0)=91 91 % 10 = 1 So 6427-30-1 is a valid CAS Registry Number.