555 (five hundred [and] fifty-five) is the natural number following 554 and preceding 556.

In mathematics

555 is a sphenic number. In base 10, it is a repdigit, and because it is divisible by the sum of its digits, it is a Harshad number. It is also a Harshad number in binary, base 11, base 13 and hexadecimal.

It is the sum of the first triplet of three-digit permutable primes in decimal:

${\displaystyle 113+131+311=555}$.

It is the twenty-sixth number such that its Euler totient (288) is equal to the totient value of its sum-of-divisors: ${\displaystyle \varphi (555)=\varphi (\sigma (555))}$.^[1]