The 4 is in the thousands column, so it is worth 4 x 1000 = four thousand.
40030
There are 90 four-digit palindromes
120
17
There are 210 4 digit combinations and 5040 different 4 digit codes.
Although the 4003 is kind of an improved 4001, still many bassists prefer the 4001, finally discontinued in the 80's. I guess it's personal preferences cause the 4003 is a great quality instrument.
4
24 = 4*3*2*1
4,008,004 - 4,004,001 = 4003
4003
4003
-2