The CAS Registry Mumber 31751-82-3 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 3,1,7,5 and 1 respectively; the second part has 2 digits, 8 and 2 respectively. Calculate Digit Verification of CAS Registry Number 31751-82: (7*3)+(6*1)+(5*7)+(4*5)+(3*1)+(2*8)+(1*2)=103 103 % 10 = 3 So 31751-82-3 is a valid CAS Registry Number.