The CAS Registry Mumber 65685-40-7 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 6,5,6,8 and 5 respectively; the second part has 2 digits, 4 and 0 respectively. Calculate Digit Verification of CAS Registry Number 65685-40: (7*6)+(6*5)+(5*6)+(4*8)+(3*5)+(2*4)+(1*0)=157 157 % 10 = 7 So 65685-40-7 is a valid CAS Registry Number.