mscroggs.co.uk
mscroggs.co.uk

subscribe

Puzzles

N

Consider three-digit integers \(N\) such that:
(a) \(N\) is not exactly divisible by 2, 3 or 5.
(b) No digit of \(N\) is exactly divisible by 2, 3 or 5.
How many such integers \(N\) are there?

Show answer & extension

If you enjoyed this puzzle, check out Sunday Afternoon Maths XVII,
puzzles about factors, or a random puzzle.

Archive

Show me a random puzzle
 Most recent collections 

Advent calendar 2025

Advent calendar 2024

Advent calendar 2023

Advent calendar 2022


List of all puzzles

Tags

matrices arrows square grids crossnumbers lists coordinates sport trigonometry shape crosswords ave sequences gerrymandering time fractions floors folding tube maps consecutive integers unit fractions geometric mean logic scales probabilty doubling ellipses christmas money digits chalkdust crossnumber pentagons percentages binary determinants square roots prime numbers coins decahedra powers sums polygons digital clocks cards functions integration rectangles sum to infinity area 2d shapes perimeter symmetry dates perfect numbers odd numbers 3d shapes partitions triangles bases numbers games square numbers tournaments pascal's triangle probability star numbers indices differentiation colouring taxicab geometry products geometry clocks calculus advent speed algebra factors quadrilaterals axes tiling rugby cubics remainders hexagons cryptic crossnumbers dominos averages xor planes chocolate graphs the only crossnumber medians irreducible numbers cryptic clues polynomials tangents sets parabolas cube numbers addition multiplication combinatorics multiples range balancing means wordplay dodecagons spheres prime factors books neighbours quadratics albgebra elections chess complex numbers regular shapes expansions geometric means shapes number angles mean routes menace palindromes triangle numbers people maths proportion lines dice squares even numbers grids surds division circles consecutive numbers factorials integers median multiplaction squares volume digital products

Archive

Show me a random puzzle
▼ show ▼
© Matthew Scroggs 2012–2026