Excel BI - Excel Challenge 721

excel-challenges

excel-formulas

🔰 Extract the prime numbers that satisfy all of these.

Published

March 24, 2026

Illustration for Excel BI - Excel Challenge 721

Challenge Description

🔰 Extract the prime numbers that satisfy all of these.

Solutions

library(tidyverse)
library(readxl)
library(arrangements)
library(primes)

path = "Excel/700-799/721/721 Prime_number_5digit.xlsx"
test = read_excel(path, range = "A1:A62")

perms <- permutations(1:9, 5) %>%
  as.data.frame() %>%
  unite("number", everything(), sep = "")

res <- perms %>%
  mutate(
    last4 = as.numeric(substr(number, 2, 5)),
    last3 = as.numeric(substr(number, 3, 5)),
    last2 = as.numeric(substr(number, 4, 5)),
    last1 = as.numeric(substr(number, 5, 5)),
    number = as.numeric(number)
  ) %>%
  filter(
    is_prime(last4) &
      is_prime(last3) &
      is_prime(last2) &
      is_prime(last1) &
      is_prime(number)
  ) %>%
  select(number)

all.equal(test, res, check.attributes = FALSE)
# [1] TRUE

Logic: Read the workbook ranges needed for the challenge; Derive the required intermediate columns; Reshape the result into the workbook output format.
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
from itertools import permutations
from sympy import isprime

test = pd.read_excel("700-799/721/721 Prime_number_5digit.xlsx", usecols="A", nrows=62)
perms = (int(''.join(map(str, p))) for p in permutations(range(1,10), 5))

def check(n):
    return all(isprime(n % 10**i) for i in range(1, 6))

res = pd.DataFrame({'number': [n for n in perms if check(n)]})
print(res['number'].equals(test['Result']))

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.