The CAS Registry Mumber 193806-54-1 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,9,3,8,0 and 6 respectively; the second part has 2 digits, 5 and 4 respectively. Calculate Digit Verification of CAS Registry Number 193806-54: (8*1)+(7*9)+(6*3)+(5*8)+(4*0)+(3*6)+(2*5)+(1*4)=161 161 % 10 = 1 So 193806-54-1 is a valid CAS Registry Number.