555 (number)

Template:One source Template:Infobox number 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.

555 is a Harshad number as 555 ÷ (5+5+5) is 555 ÷ 15 is 37. Also, 555 is unique because it is not just a multiple of 5+5+5 (15) but that 15 is divisible by its triangular order.

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

$113+131+311=555$.

It is the twenty-sixth number such that its Euler totient (288) is equal to the totient value of its sum-of-divisors: $\phi (555)=\phi (\sigma (555))$.

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