Make 64 with four 9s

The classic four nines puzzle: build an expression from exactly four 9s that equals 64. 64 cannot be made with + - × ÷, concatenation, or decimals (the solver checked every expression) — solutions need square roots, factorials, or exponents.

Solutions using only + - × ÷

No expression made of four plain 9s and + - × ÷ reaches 64 — the solver checked every possible expression.

Solutions with concatenation and decimals

Concatenation and decimals do not help for 64 either — every combination was checked.

Solutions with square roots, factorials, exponents

9 × sqrt(9)! + 9 / .9 = 64
((9 + 9) / 9) ^ sqrt(9)! = 64
((.9 + .9) / .9) ^ sqrt(9)! = 64
((9! + 9!) / 9!) ^ sqrt(9)! = 64
(9 / 9 + sqrt(9)) ^ sqrt(9) = 64

…and 124 more at this tier.

129 distinct solutions found in total, after removing trivial rearrangements.

How 64 compares

64 has 129 distinct solutions across all three tiers — #29 most plentiful of all 100 targets. Next door, 63 has 75 solutions and 65 has 6 solutions.

If 64 went down easily, make 65 with four 9s — 6 solutions, the nearest step up in scarcity.

Make 63 with four 9s · Make 65 with four 9s

The Number Lab

Same idea, different constraints: four 9s, four 4s, or any four digits you like.

Four Nines — the daily puzzle
Four Nines solver — every target, solved
Four Fours — the 1881 original
Four Fours solver — including the impossible five
Make 24 solver — any four digits
Today's 24 — one new hand a day

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Four Nines — the daily puzzle: four 9s, one target, new at midnight
The Reflex Lab — nine ways to measure your hands and memory, none of them polite about it
hand me something weird — a random pick from the directory. Could be the horse.

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