555 (number)

This article is about the integer. For the telephone number, see 555 (telephone number). For other uses, see 555 (disambiguation).

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

← 554 555 556 →
List of numbers Integers ← 0 100 200 300 400 500 600 700 800 900 →
Cardinal	five hundred fifty-five
Ordinal	555th (five hundred fifty-fifth)
Factorization	3 × 5 × 37
Greek numeral	ΦΝΕ´
Roman numeral	DLV, dlv
Binary	10001010112
Ternary	2021203
Senary	23236
Octal	10538
Duodecimal	3A312
Hexadecimal	22B16

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.^[1] 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:

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

It is the twenty-sixth number such that its Euler totient (288) is equal to the totient value of its sum-of-divisors: ${\displaystyle \varphi (555)=\varphi (\sigma (555))}$.^[2]