How do i make a define a variable as an integer in a bash shell script?

[shoebill]

Man page for builtin declare command.

declare -i LuckyNumber

LuckyNumber=5
echo Number = $LuckyNumber

LuckyNumber=five
echo Number = $LuckyNumber

Running it produces.

$ ./declare.sh
Number = 5
Number = 0

The string assigned to the variable, end up as zero.