Here’s a great set of facts about the number 73 (a Chuck Norris Number, sidenote I might grow to like that show but I can’t stand the laugh track):

• The mirror of 73, the 21st prime number, 37, is the 12th prime number. The number 21 has factors 7 and 3.
• In binary, 73 is a palindrome – 1001001
• Of the 7 binary digits representing 73, there are 3 ones.
• Every positive integer is the sum of at most 73 sixth powers.
• In octal, 73 is a repdigit – 111
• Pi Day occurs on the 73rd day of the year (March 14) on non-leap years

Many more facts to be found at this great post: http://www.walkingrandomly.com/?p=3024