2,561
2,561 is a composite number, odd.
Properties
Primality
Prime factorization: 13 × 197
Divisors & multiples
Sums & aliquot sequence
Representations
- In words
- two thousand five hundred sixty-one
- Ordinal
- 2561st
- Roman numeral
- MMDLXI
- Binary
- 101000000001
- Octal
- 5001
- Hexadecimal
- 0xA01
- Base64
- CgE=
- One's complement
- 62,974 (16-bit)
Historical numeral systems
- Babylonian (base 60)
- 𒌋𒌋𒌋𒌋𒁹𒁹 𒌋𒌋𒌋𒌋𒁹
- Egyptian hieroglyphic
- 𓆼𓆼𓍢𓍢𓍢𓍢𓍢𓎆𓎆𓎆𓎆𓎆𓎆𓏺
- Greek (Milesian)
- ͵βφξαʹ
- Mayan (base 20)
- 𝋦·𝋨·𝋡
- Chinese
- 二千五百六十一
- Chinese (financial)
- 貳仟伍佰陸拾壹
Digit at this position in famous constants
- π — Pi (π)
- Digit 2,561 = 5
- e — Euler's number (e)
- Digit 2,561 = 0
- φ — Golden ratio (φ)
- Digit 2,561 = 0
- √2 — Pythagoras's (√2)
- Digit 2,561 = 3
- ln 2 — Natural log of 2
- Digit 2,561 = 2
- γ — Euler-Mascheroni (γ)
- Digit 2,561 = 1
Also seen as
UTF-8 encoding: E0 A8 81 (3 bytes).
As an unsigned 32-bit integer, this is the IPv4 address 0.0.10.1.
- Address
- 0.0.10.1
- Class
- reserved
- IPv4-mapped IPv6
- ::ffff:0.0.10.1
Unspecified address (0.0.0.0/8) — "this network" placeholder.
This passes the ABA routing number checksum and matches the Federal Reserve numbering scheme.
Banks operate many routing numbers per state and division; an unmatched checksum-valid number can still be a real RTN at a smaller institution.
The digit sequence 2561 first appears in π at position 9,185 of the decimal expansion (the 9,185ordinal-suffix:th digit after the integer 3).
Search range: the first 1,000,000 fractional digits of π. Any 6-digit-or-shorter string is virtually guaranteed to appear in there — the more interesting signal is the position.