21,679

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Number

$21 \, 679$ (twenty-one thousand, six hundred and seventy-nine) is:

$7 \times 19 \times 163$

The $21$st non-square positive integer, and largest known, which cannot be expressed as the sum of a square and a prime:

$10$, $34$, $58$, $85$, $91$, $130$, $214$, $226$, $370$, $526$, $706$, $730$, $771$, $1255$, $1351$, $1414$, $1906$, $2986$, $3676$, $9634$, $21 \, 679$

Also see

• Previous: Non-Square Positive Integers not Sum of Square and Prime