The CAS Registry Mumber 7442-22-0 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 7,4,4 and 2 respectively; the second part has 2 digits, 2 and 2 respectively. Calculate Digit Verification of CAS Registry Number 7442-22: (6*7)+(5*4)+(4*4)+(3*2)+(2*2)+(1*2)=90 90 % 10 = 0 So 7442-22-0 is a valid CAS Registry Number.