The CAS Registry Mumber 138736-63-7 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,3,8,7,3 and 6 respectively; the second part has 2 digits, 6 and 3 respectively. Calculate Digit Verification of CAS Registry Number 138736-63: (8*1)+(7*3)+(6*8)+(5*7)+(4*3)+(3*6)+(2*6)+(1*3)=157 157 % 10 = 7 So 138736-63-7 is a valid CAS Registry Number.