The CAS Registry Mumber 124764-20-1 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,2,4,7,6 and 4 respectively; the second part has 2 digits, 2 and 0 respectively. Calculate Digit Verification of CAS Registry Number 124764-20: (8*1)+(7*2)+(6*4)+(5*7)+(4*6)+(3*4)+(2*2)+(1*0)=121 121 % 10 = 1 So 124764-20-1 is a valid CAS Registry Number.