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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

Practise with a game

Count with Me

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Place Value Quest

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Times Tables Challenge

Practise 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.