4,294,967,295

Template:Infobox number The number 4,294,967,295 is an integer equal to 2Template:Sup − 1. It is a perfect totient number. It follows 4,294,967,294 and precedes 4,294,967,296. It has a factorization of $3\cdot 5\cdot 17\cdot 257\cdot 65537$.

In geometry

Since the prime factors of 2Template:Sup − 1 are exactly the five known Fermat primes, this number is the largest known odd value n for which a regular n-sided polygon is constructible using compass and straightedge. Equivalently, it is the largest known odd number n for which the angle $2\pi /n$ can be constructed, or for which $\cos(2\pi /n)$ can be expressed in terms of square roots.

Not only is 4,294,967,295 the largest known odd number of sides of a constructible polygon, but since constructibility is related to factorization, the list of odd numbers n for which an n-sided polygon is constructible begins with the list of factors of 4,294,967,295. If there are no more Fermat primes, then the two lists are identical. Namely (assuming 65537 is the largest Fermat prime), an odd-sided polygon is constructible if and only if it has 3, 5, 15, 17, 51, 85, 255, 257, 771, 1285, 3855, 4369, 13107, 21845, 65535, 65537, 196611, 327685, 983055, 1114129, 3342387, 5570645, 16711935, 16843009, 50529027, 84215045, 252645135, 286331153, 858993459, 1431655765, or 4294967295 sides. If there are more numbers in this list, they must be at least 2Template:Sup+1 (approximately 10Template:Sup), because every intervening Fermat number is known to be composite.

In computing

The number 4,294,967,295, equivalent to the hexadecimal value Template:Nowrap, is the maximum value for a 32-bit unsigned integer in computing. It is therefore the maximum value for a variable declared as an unsigned integer (usually indicated by the Template:Code codeword) in many programming languages running on modern computers. The presence of the value may reflect an error, overflow condition, or missing value.

This value is also the largest memory address for CPUs using a 32-bit address bus. Being an odd value, its appearance may reflect an erroneous (misaligned) memory address. Such a value may also be used as a sentinel value to initialize newly allocated memory for debugging purposes.

See also

• Magic number (programming)
• 2147483647 (number)
• Power of two
• Equilateral triangle
• Pentagon
• Heptadecagon (17-sides)
• 257-gon
• 65537-gon