Advent calendar 2018

6 December

This puzzle is inspired by a puzzle that Daniel Griller showed me.
Write down the numbers from 12 to 22 (including 12 and 22). Under each number, write down its largest odd factor*.
Today's number is the sum of all these odd factors.
* If a number is odd, then its largest odd factor is the number itself.

Show answer


Show me a random puzzle
 Most recent collections 

Advent calendar 2020

Advent calendar 2019

Sunday Afternoon Maths LXVII

Coloured weights
Not Roman numerals

Advent calendar 2018

List of all puzzles


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


Show me a random puzzle
▼ show ▼
© Matthew Scroggs 2012–2021