In Japanese, numeric substitution is a common form of goroawase (語呂合わせ, "phonetic matching") by which numbers are substituted for homophonous words and phrases.
Numeric substitution may be done as wordplay, but it is more commonly used to produce abbreviations and mnemonic devices.
In Japanese, each digit/number has at least one native Japanese (kun'yomi), Sino-Japanese (on'yomi), and English-origin reading.
Furthermore, variants of readings may be produced through abbreviation (i.e. rendering ichi as i), consonant voicing (i.e sa as za; see Dakuten and handakuten), gemination (i.e. roku as rokku; see sokuon), vowel lengthening (i.e. ni as nii; see chōonpu), or the insertion of the nasal mora n (ん).
Numeric goroawase generator