7 and 21 are horrible picks, heres why. even from a non-mathematical perspective, 7's name is reason enough for shame (shame on the number, not you). 7 is the only number with 2 syllables except for 0, which is special and gets some of a pass. a number when considered from a non-mathematical perspective only encompasses the sigle digit numbers, as other numbers are just conglomerates of them. from a non-mathematical perspective, one is to look at the symbols, not what the symbols represent, but the more meaningful arguments come from the mathematical perspective. 7 is a prime number, one may think thats reason for it being ones favorite, but it is, instead, the opposite. prime numbers are definitionally hard to work with. theyre stubborn, messy, and just generally unco-operative. that makes them useful in cryptography, but in every other case its the exact number you hope not to get. compare 7 to something like 8—oh what a beutiful number, 8. 8 is extremely co-operative with fellows in the 2^n family of numbers. the 2^n family is a very special family as you can very easily and intuitively do math with them. sure 3^n numbers dont play quite as nicely with them but if u see a .3̅ you can easily unerstand that* 3 = 1. with prime numbers you cant play around with them without getting extremely messy fractions. 21 isnt quite prime but its still hard to play with in the same way primes are. 7 is actually my least favorite number—i hate 7.