Quant Boosters  Anubhav Sehgal, NMIMS Mumbai  Set 1

42 = 2 * 3 * 7
No of zeroes in 2006! will be the highest power of 7 in 2006!
[2006/7] + [2006/49] + [2006/343] = 331
as 42 in base 42 will be 10 and will be the provider of trailing zeroes