555 (number)

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

This article is about the integer. For the telephone number, see 555 (telephone number). For other uses, see 555 (disambiguation).
← 554 555 556 →
Cardinalfive hundred fifty-five
Ordinal555th
(five hundred fifty-fifth)
Factorization3 × 5 × 37
Greek numeralΦΝΕ´
Roman numeralDLV
Binary10001010112
Ternary2021203
Senary23236
Octal10538
Duodecimal3A312
Hexadecimal22B16

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:

    .

    It is the twenty-sixth number such that its Euler totient (288) is equal to the totient value of its sum-of-divisors: .[1]

    Telephone numbers

    The NANP reserves telephone numbers in many dialing areas in the 555 local block for fictional purposes, such as 1-308-555-3485.

    References
    1. Sloane, N. J. A. (ed.). "Sequence A006872 (Numbers k such that phi(k) is phi(sigma(k)).)". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2023-08-31.
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