Cardinal Number and Noun Conjugator
In English, the rules for plurals of nouns after numbers are easy. If there's only one of them, you use the singular. Otherwise, you use the plural. In Russian, it's far more complicated. The rules for declining Russian numerals are explained here following a number and noun conjugator which allows you to see any non-negative Russian numeral between 1 and 99 digits written in words and declined in all 6 cases with an optional noun to follow it.
Enter any number to decline and select a noun from the dropdown list...
You can type in any non-negative whole number you wish and select a noun from the dropdown box. As far as I'm aware and from extensive research, the numbers decline correctly.
Rules for declining Russian nouns with numbers
* For some numbers, the accusative case is always the same as the nominative while for others, it takes the nominative for inanimate nouns and the genitive for animate nouns. For animate nouns, if a number word directly before it has the accusative form matching the genitive case, that number will be treated as a genitive for declining that noun. This rule for animacy affects only the final 3 digits of a number. For numbers longer than 3-digits (see rule below), all digits further to the left of this always have the accusative matching the nominative case.
All small numbers (1-19, all multiples of 10 from 20-90 and all multiples of 100 from 100-900) decline independently from one another but all have the same case. This means that for say 934, this number is broken down into three small numbers, 900, 30 and 4 with the accusative form of each only influenced by the noun.
Declining numbers with more than 3 digits
When declining any number, whether with or without a noun, you decline each group of 3 digits separately and follow each group (except for the rightmost) with a big number. A big number is any one-word number that begins with a 1 and ends in three or more 0's. These numbers (and ноль) are true nouns complete with gender, animacy (these numbers are all inanimate) and a singular and plural form. As a result, they themselves decline in exactly the same way as other nouns after any number between 1 and 999.
This may seem really confusing to you and so I will present you with an example. Let's say we type in 4235001542 and select 'же́нщина' from the nouns list. Firstly, we split the number up into its 3-digit chunks and insert the appropriate big number after each chunk or an optional noun after the last chunk. When splitting into chunks, 4,235,001,542 in this case, only the left-most chunk is allowed to be less than 3 digits when the total number of digits is not divisible by 3, which is the case in this example.
Please see the table below which shows you each chunk followed by the correct big number or noun. The big number to add after a chunk is determined by the number of digits to the right of that chunk (always a multiple of 3) with this number of digits being equal to the number of 0's in the big number with the big number having a 1 in front of these zeros. This means that the big number will be the Russian word for 1000, 1000,000, 1000,000,000, etc. Each chunk is declined separately and independently as if they know nothing about the other chunks.
After each group is declined, you simply join each group together to get.
Obviously, the numbers have been tidied up into the correct format. For each chunk with a big number, if there's only one of them, you use that big number without any number in front of it. If there are none, then that group is not written at all. For the noun at the end, you always write it regardless of the whole number and always write the number chunk except for ноль. ноль is only ever written when there are exactly zero of that noun.
The rules above have been simplified to make it easier to understand. I feel it's best to learn some known rules combined with seeing practical examples which display the results. Being able to see what you think is right is reassurance that you interpreted the rules correctly and therefore confidence boosting.