The CAS Registry Mumber 26313-37-1 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 2,6,3,1 and 3 respectively; the second part has 2 digits, 3 and 7 respectively. Calculate Digit Verification of CAS Registry Number 26313-37: (7*2)+(6*6)+(5*3)+(4*1)+(3*3)+(2*3)+(1*7)=91 91 % 10 = 1 So 26313-37-1 is a valid CAS Registry Number.