The CAS Registry Mumber 507-72-2 includes 6 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 3 digits, 5,0 and 7 respectively; the second part has 2 digits, 7 and 2 respectively. Calculate Digit Verification of CAS Registry Number 507-72: (5*5)+(4*0)+(3*7)+(2*7)+(1*2)=62 62 % 10 = 2 So 507-72-2 is a valid CAS Registry Number.