The CAS Registry Mumber 74086-20-7 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 7,4,0,8 and 6 respectively; the second part has 2 digits, 2 and 0 respectively. Calculate Digit Verification of CAS Registry Number 74086-20: (7*7)+(6*4)+(5*0)+(4*8)+(3*6)+(2*2)+(1*0)=127 127 % 10 = 7 So 74086-20-7 is a valid CAS Registry Number.