The CAS Registry Mumber 68783-23-3 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 6,8,7,8 and 3 respectively; the second part has 2 digits, 2 and 3 respectively. Calculate Digit Verification of CAS Registry Number 68783-23: (7*6)+(6*8)+(5*7)+(4*8)+(3*3)+(2*2)+(1*3)=173 173 % 10 = 3 So 68783-23-3 is a valid CAS Registry Number.