• 255 can be written using four 4's:

255 has 8 divisors (see below), whose sum is σ = 432. Its totient is φ = 128.

The previous prime is 251. The next prime is 257. The reversal of 255 is 552.

255 = 5^{2} + 6^{2} + ... + 9^{2}.

255 is nontrivially palindromic in base 2, base 4, base 9, base 11 and base 16.

It is a Cunningham number, because it is equal to 2^{8}-1.

255 is an esthetic number in base 11, because in such base its adjacent digits differ by 1.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a 7-Lehmer number, since φ(255) divides (255-1)^{7}.

It is a cyclic number.

It is not a de Polignac number, because 255 - 2^{2} = 251 is a prime.

255 is an undulating number in base 9 and base 11.

Its product of digits (50) is a multiple of the sum of its prime divisors (25).

255 is a nontrivial repdigit in base 2, base 4 and base 16.

It is a plaindrome in base 2, base 4, base 8, base 10, base 13 and base 16.

It is a nialpdrome in base 2, base 4 and base 16.

It is a zygodrome in base 2, base 4 and base 16.

It is a self number, because there is not a number *n* which added to its sum of digits gives 255.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (251) by changing a digit.

It is a nontrivial repunit in base 2.

In principle, a polygon with 255 sides can be constructed with ruler and compass.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 7 + ... + 23.

It is an arithmetic number, because the mean of its divisors is an integer number (54).

255 is a deficient number, since it is larger than the sum of its proper divisors (177).

255 is a wasteful number, since it uses less digits than its factorization.

255 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 25.

The product of its digits is 50, while the sum is 12.

The square root of 255 is about 15.9687194227. The cubic root of 255 is about 6.3413257054.

Subtracting from 255 its sum of digits (12), we obtain a 5-th power (243 = 3^{5}).

It can be divided in two parts, 25 and 5, that multiplied together give a cube (125 = 5^{3}).

The spelling of 255 in words is "two hundred fifty-five", and thus it is an aban number.

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