(a) The greatest number of 4 digits = 9999. LCM of 2, 3, 4, 5, 6, 7 = 420 On dividing 9999 by 420, we get 339 as remainder. ∴ the greatest number of 4 digits which is divisible by 2, 3, 4, 5, 6 and 7 = 9999 – 339 =9660 ∴ the required number = 9660 + 1= 9661