Binary Warrior is the only app you'll need for converting numbers between bases. Binary Warrior supports converting numbers back and fourth from bases 2 through 36, specifically:

•Binary (Base-2)
•Ternary (Base-3)
•Quaternary (Base-4)
•Quinary (Base-5)
•Senary (Base-6)
•Septenary (Base-7)
•Octal (Base-8)
•Nonary (Base-9)
•Decimal (Base-10)
•Undecimal (Base-11)
•Duodecimal (Base-12)
•Tridecimal (Base-13)
•Tetradecimal (Base-14)
•Pentadecimal (Base-15)
•Hexadecimal (Base-16)
•Base-17
•Base-18
•Base-19
•Vigesimal (Base-20)
•Base-21
•Base-22
•Base-23
•Tetravigesimal (Base-24)
•Base-25
•Hexavigesimal (Base-26)
•Septemvigesimal (Base-27)
•Base-28
•Base-29
•Trigesimal (Base-30)
•Base-31
•Duotrigesimal (Base-32)
•Base-33
•Base-34
•Base-35
•Hexatridecimal (Base-36)

Binary Warrior also has features that other conversion apps don't, including:

•Conversion of numbers up to 64-bits in length
•Automatic conversion as you type
•Customized keyboard for each number base
•A variety of sharing options, including printing, email, copy, Facebook and Messages (copy, Facebook and Messages requires iOS 6 or greater)
•Error checking

Thank you for looking!