The CAS Registry Mumber 136801-04-2 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,3,6,8,0 and 1 respectively; the second part has 2 digits, 0 and 4 respectively. Calculate Digit Verification of CAS Registry Number 136801-04: (8*1)+(7*3)+(6*6)+(5*8)+(4*0)+(3*1)+(2*0)+(1*4)=112 112 % 10 = 2 So 136801-04-2 is a valid CAS Registry Number.