The CAS Registry Mumber 56017-63-1 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 5,6,0,1 and 7 respectively; the second part has 2 digits, 6 and 3 respectively. Calculate Digit Verification of CAS Registry Number 56017-63: (7*5)+(6*6)+(5*0)+(4*1)+(3*7)+(2*6)+(1*3)=111 111 % 10 = 1 So 56017-63-1 is a valid CAS Registry Number.