The CAS Registry Mumber 107659-41-6 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,0,7,6,5 and 9 respectively; the second part has 2 digits, 4 and 1 respectively. Calculate Digit Verification of CAS Registry Number 107659-41: (8*1)+(7*0)+(6*7)+(5*6)+(4*5)+(3*9)+(2*4)+(1*1)=136 136 % 10 = 6 So 107659-41-6 is a valid CAS Registry Number.