Digital root

func digroot (r, base = 10) {
    var root = r.base(base)
    var persistence = 0
    while (root.len > 1) {
        root = root.chars.map{|n| Number(n, 36) }.sum.base(base)
        ++persistence
    }
    return(persistence, root)
}
 
var nums = [5, 627615, 39390, 588225, 393900588225]
var bases = [2, 3, 8, 10, 16, 36]
var fmt = "%25s(%2s): persistance = %s, root = %2s\n"
 
nums << (550777011503 *
         105564897893993412813307040538786690718089963180462913406682192479)
 
bases.each { |b|
    nums.each { |n|
        var x = n.base(b)
        x = 'BIG' if (x.len > 25)
        fmt.printf(x, b, digroot(n, b))
    }
    print "\n"
}

Output:

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