Convert a list to an integer

Here are three ways to do it. The first is the best I think:

FromDigits@Flatten[IntegerDigits /@ {5, 22, 4, 5}]

ToExpression@StringJoin[ToString /@ {5, 22, 4, 5}]

ToExpression@StringJoin@StringCases[Characters@ToString@{5, 22, 4, 5}, DigitCharacter]

FromDigits @ ToString @ Row @ {5, 22, 4, 5}

Head[%]

52245

Integer

ToExpression@StringJoin@IntegerString[{5, 22, 4, 5}]

52245

ToExpression@StringJoin@IntegerString[{5, 22, 4, 5},#]&/@{2,10,16}

{10110110100101, 52245, 51645}