The CAS Registry Mumber 135854-65-8 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,3,5,8,5 and 4 respectively; the second part has 2 digits, 6 and 5 respectively. Calculate Digit Verification of CAS Registry Number 135854-65: (8*1)+(7*3)+(6*5)+(5*8)+(4*5)+(3*4)+(2*6)+(1*5)=148 148 % 10 = 8 So 135854-65-8 is a valid CAS Registry Number.