Excel BI - Excel Challenge 669

excel-challenges

excel-formulas

🔰 Tech Number - A number is a tech number if it has even number of digits and square of sum of first half and last half is equal to number itself.

Published

March 24, 2026

Illustration for Excel BI - Excel Challenge 669

Challenge Description

🔰 Tech Number - A number is a tech number if it has even number of digits and square of sum of first half and last half is equal to number itself. List the first 10 Tech Numbers.

Solutions

library(tidyverse)
library(readxl)

path <- "Excel/669 Tech Numbers.xlsx"
test <- read_excel(path, range = "A1:A11") %>% pull()

is_tech_number <- function(n) {
    num_str <- as.character(n)
    len <- str_length(num_str)
    if (len %% 2 != 0) return(FALSE)
    half_len <- len / 2
    h1 <- as.integer(substr(num_str, 1, half_len))
    h2 <- as.integer(substr(num_str, half_len + 1, len))
    (h1 + h2)^2 == n
}

find_tech_numbers <- function(count = 10) {
    tech_numbers <- (1:10^4)^2 %>%
        keep(~ str_length(.) %% 2 == 0 && is_tech_number(.))
    head(tech_numbers, count)
}

result = find_tech_numbers(10)
all.equal(result, test, check.attributes = FALSE)
#> [1] TRUE

Logic: Read the workbook ranges needed for the challenge.
Strengths: The code maps the workbook rule into a compact, reproducible pipeline.
Areas for Improvement: The solution assumes the workbook layout and selected ranges remain stable, so any structural change in the sheet would require small adjustments.
Gem: The elegant part is how little code is needed once the correct intermediate representation is chosen.

import pandas as pd

path = "669 Tech Numbers.xlsx"
test = pd.read_excel(path, usecols="A", nrows=10).fillna("").to_numpy().flatten().tolist()

tech_numbers = []
n = 10
while len(tech_numbers) < 10:
    if len(str(n)) % 2 == 0:
        h1, h2 = int(str(n)[:len(str(n))//2]), int(str(n)[len(str(n))//2:])
        if (h1 + h2) ** 2 == n:
            tech_numbers.append(n)
    n += 1

print(tech_numbers == test)

The Python version keeps the algorithm explicit, which helps when the challenge depends on a greedy or iterative rule.

Difficulty Level

Easy / Medium

The business rule is clear, though the workbook still needs a few transformation steps to reach the expected output.