21 (ennamba)

Abiri mu emu

21 (amakumi abiri mu gumu) oba (abiri mu emu) ye namba ey’obutonde egoberera 20 n’ekulembera 22.

Ekyasa ekiriwo kati kyasa 21 AD, wansi wa kalenda ya Gregorian.

Okubala

Amakumi abiri mu gumu ye semiprime ey’okutaano ey’enjawulo, n’ekyokubiri eky’ekifaananyi 3 x q ewali q nga ye prime eya waggulu. Ye repdigit mu quaternary (111₄).

Ebifo

Nga semiprime, 21 erina abigabanya ebituufu 1, 3 ne 7, abiri mu emu erina omugatte gwa aliquot prime ogwa 11 munda mu nsengekera ya aliquot erimu namba emu yokka ekwataganye (21, 11, 1, 0). 21 ye mmemba asooka ow’ekibinja ekyokubiri ekya semiprimes ezitali zimu eziddiring’ana (21, 22), awali ekibinja eky’engeri eyo ekiddako (33, 34, 35). Waliwo namba ezisookerwako 21 nga zirina digito 2. Waliwo namba enkulu 21 eziri wakati wa 100 ne 200.

21 ye namba enzijuvu ya Blum esooka, okuva bwe kiri nti ye semiprime nga ensonga zaayo zombi prime ze prime za Gaussian.

Nga 21 ye namba ya triangle ey’omukaaga, era ye mugatte gw’abagabanya namba enzijuvu ettaano ezisooka:

$1+2+3+4+5+6=21$

$1+(1+2)+(1+3)+(1+2+4)+(1+5)=21$

21 era ye namba esooka ey’enjuyi omunaana etali ya makulu. Ye nnamba ya Motzkin ey’okutaano, n’ennamba ya Padovan ey’ekkumi n’omusanvu (ekulembeddwamu ebigambo 9, 12, ne 16, nga ye mugatte gw’ebibiri ebisooka ku bino).

21 ye namba ey’obutonde esinga obutono etasemberera maanyi ga biri (2ⁿ), awali ebanga ly'okumpi ${\displaystyle \pm {n}.}$

Mu decimal, 21 ye namba ya Harshad ey’ekkumi n’ennya. Kye kyokulabirako ekisinga obutono ekitali kya makulu mu base ten eya namba ya Fibonacci (nga 21 ye mmemba ow’omunaana, nga omugatte gw’ebigambo ebisoose mu nsengekera 8 ne 13) nga digito zazo (2, 1) namba za Fibonacci ate nga omugatte gwa digito gwazo nagwo namba ya Fibonacci (3). Era ye namba enzijuvu ennungi esinga obunene ${\displaystyle n}$ mu decimal nga ku namba zonna enzijuvu ennungi wa ${\displaystyle a+b=n}$ ${\displaystyle a+b=n}$, waakiri emu ku ${\displaystyle {\tfrac {a}{b}}}$ ne ${\displaystyle {\tfrac {b}{a}}}$ ye decimal ekoma; laba obukakafu wansi:

Okukola square ku square

Amakumi abiri mu gumu gwe muwendo ogusinga obutono ogwa square ez’obunene obw’enjawulo ezeetaagisa okukola square.

Obuwanvu bw’enjuyi za square zino bwe buno: ${\displaystyle \{2,4,6,7,8,9,11,15,16,17,18,19,24,25,27,29,33,35,37,42,50\}}$

ezikola omugatte gwa 427 nga tobaliddeemu square y’obuwanvu bw’oludda ${\displaystyle 7};$omugatte guno gukiikirira namba enzijuvu esinga obunene etaliimu square ku field ya quadratic eya kiraasi namba bbiri, nga 163 gwe muwendo ogusinga obunene ogw’ekika kino (Heegner) ogwa kiraasi emu.

Matrix za kkuudratiki mu Z

Namba ya prime ey’amakumi abiri mu emu 73 ye mmemba esinga obunene mu matriksi ya Bhargava eya definite quadratic 17–integer matrix ${\displaystyle \Phi _{s}(P)}$ ekiikirira namba zonna ezisookerwako:${\displaystyle \Phi _{s}(P)=\{2,3,5,7,11,13,17,19,23,29,31,37,41,43,47,67,\mathbf {73} \},}$

Namba ekwataganye ey’amakumi abiri mu emu 33 ye mmemba asinga obunene mu quadratic matriksi ya namba 7, ${\displaystyle \Phi _{s}(2\mathbb {Z} _{\geq 0}+1)=\{1,3,5,7,11,15,\mathbf {33} \}}$

ekiikirira namba zonna ezitali zimu.

Emyaka 21

• Mu nsi kkumi na ssatu, 21 gwe myaka egy’okukula. Laba ne: Okujja mu myaka.
• Mu nsi munaana, emyaka 21 gy’emyaka egisinga obutono okugula ebintu ebikolebwa mu taaba.
• Mu nsi kkumi na musanvu, emyaka 21 gy’emyaka gy’okunywa.
• Mu mawanga mwenda, gwe myaka gy’okulonda.
• Mu Amerika:

1. 21 gwe myaka emitono omuntu gy’ayinza okuzannya zzaala oba okuyingira mu kazino mu masaza agasinga obungi (okuva omwenge bwe gutera okuweebwa).
2. 21 gwe myaka egisinga obutono okugula emmundu oba amasasi g’emmundu mu mateeka ga federo.
3. Mu masaza agamu, emyaka 21 gye gisinga obutono okuwerekera ddereeva omuyizi, kasita omuntu alabirira omuyizi aba ng’alina pamiti enzijuvu okumala ekiseera ekigere. Laba ne: Olukalala lw’emyaka emitono egy’okuvuga.

Mu mizannyo

Mu NASCAR, 21 ebadde ekozesebwa kkampuni ya Wood Brothers Racing ne Ford okumala emyaka mingi. Ttiimu eno ewangudde empaka za NASCAR Cup Series 99, ng’abasinga obungi bawangudde 21, ne Daytona 500 5.

Mu bintu ebirala

Mu guinea mulimu sillingi 21. Waliwo amasasi 21 agakubiddwa mu saluti y’emmundu 21 nga bassa ekitiibwa mu baami oba abakulembeze b’amawanga.

21 ekwatagana ne profile 21 (mu Yisirayiri, okuwandiika profile y’amagye ekkiriza okusonyiyibwa okuva mu buweereza bw’amagye).

21 nnamba nkulu nnyo mu maka g’emizannyo gya kaadi nga abiri mu gumu oba blackjack.