Numbers & Place Value

The Millionaire's Mansion

Two identical digits, two different values, decided by the room.

Number Translators

Switch between '45,300' and 'Forty-Five Thousand, Three Hundred' instantly.

The Multiplier Engine

See that 4,572 is really 4,000 + 500 + 70 + 2, its true blueprint.

The Vertical Stack

Count the digits first, then scan left to right for the first difference.

The Target and the Neighbour

Find the nearest friendly number using the neighbour digit rule.

Roman Numerals

Seven letters that work as numbers: add them, or subtract the small ones.