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31 in words

31

thirty-one

31 is written thirty-one.

Ways to write it

As an ordinal: thirty-first
Roman numeral: XXXI
Expanded form: 30 + 1

Place value

Place	Digit	Value
tens	3	30
ones	1	1

Number facts

Even or odd: Odd
Prime or composite: Prime
Factors: 1 and 31 (2 factors)
First 10 multiples: 31, 62, 93, 124, 155, 186, 217, 248, 279, 310
Square: 31 × 31 = 961
Square root: ≈ 5.57
Sum of the digits: 3 + 1 = 4
Rounded to the nearest 10: 30
Number before: 30
Number after: 32
In binary: 11111

Quick check

What number comes just after 31?
Show the answer
32
Is 31 even or odd?
Show the answer
Odd
What is 31 + 10?
Show the answer
41

Practice with a game

Count with Me

Count pictures up to 5, 10 or 20 and compare groups.

Place Value Quest

Ones, tens, hundreds and thousands.

Times Tables Challenge

Practice any times table from 2× to 12×.

Frequently asked questions

How do you write 31 in words?

31 is written "thirty-one".

Is 31 a prime number?

Yes. 31 is a prime number: its only factors are 1 and 31.

What are the factors of 31?

The factors of 31 are 1 and 31.

How do you write 31 in Roman numerals?

31 in Roman numerals is XXXI.