Factors of 19
The factors of 19 are 1, 19. 19 is a prime number: its only factors are 1 and itself. Prime factorisation: 19.
All 2 factors of 19
1, 19
A factor divides 19 exactly, with no remainder. Every factor has a partner: the pairs below multiply to 19. The negative factors are -1, -19, because a negative times a negative is positive.
Factor pairs of 19
| Pair | Product |
|---|---|
| 1 × 19 | 19 |
Stop at the square root (4): every pair after that is one you already have, the other way round.
Prime factorisation of 19: 19
| Divide | by the smallest prime | Result |
|---|---|---|
| 19 | 19 | 1 |
So 19 = 19.
The number of factors comes from the exponents: (1 + 1) = 2.
How to find the factors of 19
- Start with 1 and 19: every number has those two.
- Test 2, 3, 4, … up to the square root of 19, which is about 4.
- Each time a number divides exactly, write it down with its partner (the quotient).
- Use the divisibility rules to skip work: by 2 no (the last digit is odd); by 3 no (the digit sum is 10); by 5 no (the last digit is 9).
- Put the list in order: 1, 19.
🧮 Calculator
The answer appears here, with the working in words.
✏️ Five questions, answers hidden
1. List the factors of 20.
Answer: 1, 2, 4, 5, 10, 20
2. Write the prime factorisation of 38.
Answer: 2 × 19
3. How many factors does 19 have?
Answer: 2
4. What is the largest factor of 19 other than itself?
Answer: 1
5. Is 21 prime or composite?
Answer: composite
📚 The class this belongs to
Factors are taught in Grade 4 and 5 in the US, Year 5 and 6 in the UK, Class 4 to 6 in CBSE (NCERT Class 6, Playing with Numbers) and Year 5 and 6 in Australia.
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