As part of the Igbo Izugbe project, the Society for Promoting Igbo Language and Culture (Otu Iwelite Asụsụ na Omenaala Igbo) developed the standard Igbo numbering system. They achieved this by borrowing from various Igbo dialects, and ensuring the numbering system is decimal. They also ensured only addition is used, subtraction is not used. For example, 19 is now iri na otu (ten plus one), instead of bere otu n'ọgụ (twenty minus one). This numbering system is recommended for teaching in schools, it does not replace the numbering systems in various dialects.
Another important feature of this numbering system is that it can be used to count to millions and even trillions. Before this development, the numbering systems in most Igbo dialects could only count to thousands, and after that it becomes nnụ kwuru nnụ kwuru nnụ... (four hundreds upon four hundreds upon four hundreds...), or agụta agụta (uncountable).
This numbering system also accommodates variations in dialects while maintaining the decimal system. For example, the number one can be otu or ofu; number two can be abụọ, ịbụọ, abụa, ịbụa, number three can be atọ, ịtọ, ntọ; number four can be anọ, ịnọ, nnọ; number six can be isii, ishii; number seven can be asaa, ịsaa; number eight can be asatọ, ịsatọ; number nine can be itoolu, teghete, iteghete, itenaanị; number ten can be iri, ili.
Another important feature of this numbering system is that it can be used to count to millions and even trillions. Before this development, the numbering systems in most Igbo dialects could only count to thousands, and after that it becomes nnụ kwuru nnụ kwuru nnụ... (four hundreds upon four hundreds upon four hundreds...), or agụta agụta (uncountable).
This numbering system also accommodates variations in dialects while maintaining the decimal system. For example, the number one can be otu or ofu; number two can be abụọ, ịbụọ, abụa, ịbụa, number three can be atọ, ịtọ, ntọ; number four can be anọ, ịnọ, nnọ; number six can be isii, ishii; number seven can be asaa, ịsaa; number eight can be asatọ, ịsatọ; number nine can be itoolu, teghete, iteghete, itenaanị; number ten can be iri, ili.
1 - otu
2 - abụọ
3 - atọ
4 - anọ
5 - ise
6 - isii
7 - asaa
8 - asatọ
9 - itoolu
10 - iri
11 - iri na otu
12 - iri na abụọ
13 - iri na atọ
14 - iri na anọ
15 - iri na ise
16 - iri na isii
17 - iri na asaa
18 - iri na asatọ
19 - iri na itoolu
20 - iri abụọ
21 - iri abụọ na otu
22 - iri abụọ na abụọ
23 - iri abụọ na atọ
24 - iri abụọ na anọ
25 - iri abụọ na ise
26 - iri abụọ na isii
27 - iri abụọ na asaa
28 - iri abụọ na asatọ
29 - iri abụọ na itoolu
30 - iri atọ
31 - iri atọ na otu
39 - iri atọ na itoolu
40 - iri anọ
50 - iri ise
60 - iri isii
70 - iri asaa
80 - iri asatọ
90 - iri itoolu
100 - otu narị
101 - otu narị na otu
111 - otu narị na iri na otu
200 - narị abụọ
300 - narị atọ
400 - narị anọ
600 - narị isii
800 - narị asatọ
900 - narị itoolu
1,000 - otu puku
1,001 - otu puku na otu
1,649 - otu puku, nari isii, iri ano na itoolu
2,000 - puku abụọ
3,000 - puku atọ
6,821 - puku isii, narị asatọ, iri abụọ na otu
8,000 - puku asatọ
10,000 - puku iri
50,000 - puku iri ise
52,800 - puku iri ise, puku abụọ na narị asatọ
99,999 - puku iri itoolu na puku itoolu, na narị itoolu, iri itoolu na itoolu
100,000 - narị puku
680,722 - puku narị iri isii, puku iri asatọ, narị asaa na iri abụọ na abụọ
900,000 - puku narị itoolu
1,000,000 - otu nde
2,000,000 - nde abụọ
6,000,000 - nde isii
7,243,641 - nde asaa, puku narị abụọ, puku iri anọ na puku atọ, narị isii na iri anọ na otu
7,821,345 - nde asaa, puku narị asatọ, puku iri abụọ na otu puku, narị atọ na iri anọ na ise
100,000,000 - otu nde narị
321,546,009 - nde narị atọ, nde iri abụọ na otu nde, puku narị ise, puku iri anọ na puku isii na itoolu
400,000,000 - nde narị anọ
1,000,000,000 - nde puku
1,000,000,000,000 - otu ijeri
Other numbers
20 - ohu
20 - ọgụ
25 - ọgụ na ise
39 - bere otu n'ohu abụọ
400 - nnụ
1⁄2 - ọkara
3⁄4 - atọ n'ime anọ
100 - ọgụ ise
200 - ọkara nnụ
600 - nnụ na ọkara
1000 - nnụ abụọ na ọkara
8,000 - ohu nnụ
0 - efu
Igbo Ordinal numbers
Ordinal numbers are achieved in Igbo language by writing or saying nke before the cardinal numbers (with the exception of first, where mbụ or izizi is used in place of the cardinal number otu). So, first is nke mbụ or nke izizi. In fact, for first and first only, the ordinal number can be mbụ or izizi, without nke.
1st - nke mbụ
2nd - nke abụọ
3rd - nke atọ
4th - nke anọ
5th - nke ise
6th - nke isii
7th - nke asaa
8th - nke asatọ
9th - nke itoolu
10th - nke iri
Quantifiers
Numbers can also be used as quantifiers. For example, 'two people came' is 'mmadụ abụọ bịara'. As quantifier, we say 'mmadụ naabụ bịara'.
1 - -
2 - naabọ (naabụ)
3 - naatọ
4 - naanọ
5 - neese
6 - neesii
7 - naasaa
8 - naasatọ
9 - neeteghete
10 - neeri
Item Counting
When counting items in the presence of another person, and the items are not more than ten, the following numbers can be used.
1 - nnaa
2 - mbọọ
3 - ntọ
4 - nnọ
5 - ise
6 - isii
7 - asaa
8 - asatọ
9 - iteghete
10 - iri