Does it handle Russian gender and plural rules?

Yes. It uses одна/две for the feminine тысяча, and picks the right plural form — тысяча, тысячи or тысяч — based on the standard Russian 1 / 2-4 / 5+ agreement rule.

How large a number can I convert?

Up to 12 digits in the integer part, which covers values into the billions (миллиарды).

Why does тысяча change to тысячи and тысяч?

Russian nouns after numbers take one of three forms by the standard agreement rule: the singular after 1 (одна тысяча), the genitive singular after 2-4 (две тысячи), and the genitive plural after 5 and above (пять тысяч). The same applies to миллион and миллиард.

Why is 1 sometimes один and sometimes одна?

The number 1 agrees in gender with the following word. Before the feminine тысяча it becomes одна; before миллион and миллиард it stays masculine один.

Is anything sent to a server?

No. The conversion runs entirely in your browser — no number you type ever leaves your device.

Number to Words in Russian

This tool spells any whole number into Russian words, applying the language’s grammatical gender and plural agreement automatically. It runs entirely in your browser.

How it works

Each three-digit group is spelled and joined to its scale word — тысяча (thousand), миллион (million), миллиард (billion). Two agreement rules are applied:

Gender — the number 1 (and 2) agree with the feminine тысяча, so it becomes одна/две rather than один/два.
Plural form — the scale word takes the standard 1 / 2-4 / 5+ endings: тысяча after 1, тысячи after 2-4, and тысяч after 5 and above.

Example

Number	Russian
1,000	одна тысяча
2,000	две тысячи
5,000	пять тысяч

So 1234 spells out as одна тысяча двести тридцать четыре.

Everything happens in your browser. Nothing you type is uploaded anywhere.