Significance of numbers in Vedic culture

In a recent conversation, a good friend of mine asked "why chant gAyatri japa in multiples of 12, like 12, 48, 108 etc". I made an attempt to explain the logic and beauty of numbers in the vedic culture. However I realized that there is much more than just this and Sri Bannanje Govindacharya has written an entire book on the significance of numbers in spiritual pursuit. I am recollecting some of those that can mesmerize even the most educated ones. Here is my interpretation and understanding, based on what I have read, heard, contemplated and understood..

Regarding the question "why 12" (or any other number for that matter): the idea is not about 12 or any other number but about "poorNatva" - the "completeness" or "fullness". Vedic culture has provided a perspective as to what makes something complete and that is through sankhya - or logic or numbers. Let us take a look at some significant numbers and what they represent:

• 1 - ekamEvAdviteeyaM brahma: 1 represents that there is only one Lord above all. He is 1, the starting point of everything that is. The AUM the ekAkshara (aum ityekAksharam brahma (Gita 8.13).
  
• 2 - prakriti-purusha: from the 1 comes the 2, which represents the nature of His creation; the duality in nature - brahmANDa-piNDANda, chetana-achetana, nAma-roopa, chara-achara, sthoola-sookshma, kArya-kAraNa, moorta-amoorta, bhAva-abhAva, sukha-dukha, male-female, day-night, cold-dark, old-young etc; krishna-paksha (15 days of the 'waning' moon) and shukla paksha (15 days of the 'growing' moon)
  
• 3 - triguNa: The 2 has qualities that are 3, represented in many ways:
• asti - jada, jeeva, eeshvara
• guNa - satva (goodness), rajas (passion), tamas (ignorance or darkness)
• kAla - bhoota (past), vartamAna (present), bhavishyat (future) 
• shakti - jnAnashakti, icchAshakti, kriyAshakti
• lOka - bhoo, bhuva, svaH
• akshara - aum'kAra's 'a', 'u', 'ma'
• vacahana - eka, dwi, bahu
• purusha - prathama, madhyama, utthama
• avastha - sRuShTi, sthiti, laya
• piNDa-avastha - jAgrat, swapna, sushupti
• trimurti - brahma vishnu maheshvara
  
• 4 chaturmukha 
• 4 purushArtha (aims of existence) - dharma (duty, righteousness, ethical living), artha (wealth, purpose), kAma (desire, aspirations, progeny), mOksha (liberation, freedom)
• 4 veda samhitAs (sciences) - rik, yajur, sAma, atharva
• 4 shriti varNAs - shukla, rakta, peeta, kRushNa 
• 4 varNa - brAhmaNa, kshatriya, vaishya, shudra
• 4 aashramAs - brahmacharya, grAhasthya, vAnaprastha, saMnyAsa
• 4 vRuttis - anveekshikee, trayee, vaartaa, daMDaneeti
• 4 upavedAs - aayurveda, dharnurveda, gAMdharvaveda, sthApatyaveda
• 4 approaches - sAma (appeasing, conciliating, mild means), dAna ('giving in', teaching, charity, being liberal), bheda (contrasting, splitting, dividing, seducing, divulging, breach, betraying), danDa (punishing, giving a stick, displaying authority, fining, chastising)
  
• 5 represents
• 5 bhoota - pRuthvi (earth), aapas (water), tEjas (fire), vAyu (air), and aakaasha or kham (space)
• 5 indriyAs - eyes, ears, tongue, nose, and skin
• 5 tanmAtra - gandha, rasa, roopa, sparsha, shabda
• 5 karmendriyAs - vAk, vANi, pAda, pAyu, upastha
• 5 antahkaraNa - manassu, buddhi, ahaMkAra, chitta, chetana
• 5 prANAs - vital air or humor within - prANa, apAna, vyAna, udAna, samAna 
• 5 kOshAs - annamaya, prANamaya, manomaya, vijnAnamaya, aanandamaya
• 5 rutus - vasanta, greeshma, varsha, sharat, hEmaMta shishira (in the vedic sampradAya hemanta and shishira are considered one) 
• 5 kanyAs - ahalyA, draupadi, seetA, kunti, tAra, mandodari
  
• 6 Represents 
• 6 bhAvavikAra - bhrooNa (fetal), janana (birth), vRuddhi (growth), vikRuti / parivartana (changes, transformations), kshati (damage), mrutyu (death)
• 6 upAsanA guNAs - aishwarya, veerya, yashas, shree, jnAna, vairAgya
• 6 states - shoka, mOha, ashana (hunger), trisha (thirst), jara (old age), rOga (disease)
• 6 arishadvargAs (enemies) - kAma, krodha, lObha, mOha, mada, mAtsarya
• 6 bhagavad vritti karmAs - yajana, yAjana, dAna, pratigraha, adhyayana, adhyApana
• 6 vedAngAs - sheekshA, kalpa, vyAkarNa, nirukta, jyotiSha, chandas
  
• 7 Represents
• 7 saptadhAtus - tvak (outer skin), charma (inner shield), mAmsa (flesh), rakta (blood), peena (fat), asti (bone), majja (marrow) 
• 7 saptarishis - mareechi, atri, amgiras, pulastya, pulaha, kratu, vasiShTha
• 7 manvantara saptarishis - kAshyapa, atri, vasiShTha, vishvAmitra, gautama, jamadagni, bharadvAja
• 7 saptasvarAs - ShaDja, RuShabha, gAMdhAra, madhyama, paMchama, daivata, niShAda (sa, ri, ga, ma, pa, da, ni, sa)
• 7 saptaChandas - gAyatri for ShaDja, uShNik for RuShabha, anuShTap for gAMdhAra, bRuhati for madhyama, paMkti for paMchama, triShTup for dhaivata, jagatee for niShAda
• 7 jvAlAs - kALee, karALee, manojavA, sulOhitA, sudhoomravarNa, spuliMginee, vishvaruchee
• 7 vArAs (representing the influential graha) - bhAnu, sOma, maMgaLa, budha, guru, shukra, shani 
• 7 higher lOkAs - bhooH, bhuvaH, svaH, mahaH, janaH, tapaH, satyam
• 7 lower lOkAs - ataLa, vitaLa, sutaLa, taLAtaLa, mahAtaLa, rasAtaLa, pAtALa
• 7 sAgarAs - lavaMa (salty), ikShu (sugarcane, sweet), surA (spirituous, wine) , ghRuta (ghee), dadhi (curd), ksheera (milk), shuddhOdaka (fresh water)
• 7 adhyAtma chakra or glands - moolAdhAra (gonald), svAdhiShTAna (cells of Leydig), maNipoora (Adrenal), anAhata (Thymus), vishuddhi (Thyroid and Parathyroid), ajnA (Pineal), sahasrAra (Pituitary)
• 7 mahAparvatAs - himavanta, mEru, hEmakooTa, niShadha, mAlyavaMta, gaMdhamAdana, pAriyAtra 
• 7 mahAnadi - gaMgA, yamunA, saraswati, gOdAvari, narmadA, sidhu, kAvEri 
• 7 saptamAtrikAs - brahmaNi, mAheshvari, mAheshvari, kaumAri, vaishNavi, varAhi, indrANi, chAmuNda
  
• 8 Represents
• 8 asthAksharAs in AUM - akAra, ukAra, makAra, nAda, biMdu, kale, shAMta, atishAMta
• 8 nArAyaNAkshara - "Om namo nArAyaNAya"
• 8 bhagawanta roopa - vishva, taijas, prAjna, tureeya, aatma, antarAtma, paramAtma, jnAnAtma
• 8 akshara vargAs (alphabetical categories) - svrAksharAs (16), kavarga, chavarga, Tavarga, tavarga, pavarga, aMtasthAkshara (ya, ra, la, va), antAksharAs (sha, Sha, sa, ha, La, ksha)
• 8 vidha prakRuti - ahaMkAra, buddhi, manas, aakAsha, vAyi, agni, anila, pruthvi
• 8 jeevA varga - devatAs, gaMdharvAs, dAnavAs, rAkshasAs, pishAchAs, mAnushAs, tiryagjaMtoos, sthAvarAs
• 8 vasus - droNa (dhara), prANa, dhruva, arka, agni, dOSha, vastu, vibhAvasu
• 8 diks (directions with their deities) - poorva (east; mitra or Indra), aagneya (agni), dakshiNa (yama), naiRutya (nirRuti), paschima (varuNa), vAyuvya (vAyu), uttara (chandra, kubEra), aishAnya (eeshAna)
• 8 diggajAs (great elephants) - airAvata, puMDareeka, vAmana, kumuda, anjana, puShpadaMta, saarvabhauma, suprateeka
• 8 diggajAs' female consorts -  abhramu, kapilA, piMgaLa, anupamA, tAmrakarNi, shubhradaMti, aMganA, aMjanAvati 
• 8 ashtAnga yOga - yama, niyama, aasana, prANAyAma, pratyAhAra, dhAraNA, dhyAna, samAdhi
• 8 aishwaryAs or siddhis through yOgadhAraNa -  aNimA (becoming smaller than an aNu - atom), mahimA (becoming heavier than a hill, larger than a mountain), laghimA (becoming lighter than a grass blade or a cotton ball), prApti (garnering anything through anyone), prAkAshya (sarvajnatva, ability to comprehend everything), eeshitva (multiplying one's abilities to enormous amounts), vashitva (charming others and overcoming any obstacle), prAkAmya (experiencing any desired pleasure); some include garima over prAkAshya, and some include both and make it 9 siddhis.
• 8 aayurveda ashtAmgAs - shalya chikitse (surgery), shAlAkya chikitse (ENT), kAya chikitse (Physiotherapy), bhoovidye (freeing one from 'bhootabAdhe' or psychological disturbances), kaumArabRutya (gynecology and pediatrics), aagadataMtra (viShavaidyaka; treating poisoning), rasAyana taMtra (deerghAyurArOgya sAdhana; creating mixtures for long life), vAjeekaraNataMtra (veeryavardhana prayOga; increasing fertility and virility)
• 8 sAshTAnga namaskAra - prostration using 8 aspects of the body - legs, knees, hands, chest, head, respectful sight,  praising words, and revering mind 
• 8 vivAha vidhAs - brahmavivAha, daivavivAha, aarShavivAha, prAjApatyavivAha, gAMdharvavivAha, aasuravivAha, raakshasavivAha, paishAchavivAha. 
• First four are by the blessings of the elder and parents, conducting by them
• gAMdharva - by mutual agreement between bride and groom
• aasuravivAha - enticed by money, out of greed for money 
• Last two are forced marriages without consent of the other party  
• 8 ashtamadAs - roopamada (intoxicated by beauty), yauvanamada (intoxicated by youthfulness), streemada (intoxicated by the opposite sex), dhanamada (intoxicated by wealth), vidyAmada (intoxicated by knowledge), kulamada (intoxicated by family lineage), annamada (intoxicated by overeating), udyOgamada (intoxicated by professional status)
  
• MORE TO FOLLOW ....