Is 15 a prime number? Prime numbers are natural numbers greater than 1 that have exactly two distinct positive divisors. The answer is clear: "15 is not a prime number." As the product of two primes and a triangular number, 15 holds special significance in mathematics and appears in various real-world contexts. Let's examine why.
- Is 15 a prime number? - No
- Is 15 a composite number? - Yes
- Is 15 a perfect square? - No
- Is 15 a perfect cube? - No
- Prime Factors of 15 - 3, 5
- Factors of 15 - 1, 3, 5, 15
Is 15 a Prime or Composite Number?
Is 15 a Prime Number?
No, 15 is not a prime number. It fails the requirements for primality:
- It has more than two distinct positive divisors (1, 3, 5, 15)
- It can be expressed as a product of smaller natural numbers (3 × 5)
Why is 15 a Composite Number?
15 holds several special mathematical properties:
- It's the product of two consecutive primes (3 × 5)
- It's a triangular number (1 + 2 + 3 + 4 + 5 = 15)
- It's a hexagonal number and a pentatope number
- It's the atomic number of phosphorus (P) on the periodic table
- It's the magic constant for the smallest magic square (3×3)
Is 15 a Special Number?
Yes, 15 is special because:
- It's the smallest number that can be expressed as the sum of three consecutive primes (3 + 5 + 7)
- It's the number of days in each of the 24 cycles of the Chinese calendar
- It appears in the famous "15 puzzle" sliding game
Problem Statements:
| Property | Answer |
|---|---|
| Is 15 a Prime Number? | No |
| Is 15 a Composite Number? | Yes |
| Is 15 a Perfect Square? | No |
| Is 15 an Even Number? | No |
| Multiples of 15 | 15, 30, 45, 60, 75, 90, 105, 120, 135, 150,... |
| Square Root of 15 | ≈3.87298 |
| Square of 15 | 225 |
| Is 15 a Perfect Cube? | No |
| Cube Root of 15 | ≈2.46621 |
| Is 15 an Odd Number? | Yes |
Fun Facts:
- 15 is the legal drinking age in many countries
- In rugby union, 15 players take the field for each team
- The 15th amendment to the U.S. Constitution granted voting rights regardless of race
- Quinceañeras celebrate a girl's 15th birthday in Latin American cultures
- There are 15 players on a doubles tennis team in the Davis Cup
- In tarot, card XV is The Devil (representing materialism and bondage)
- The human body has 15 pairs of ribs (30 total) in about 8% of the population
- 15 is the number of minutes in a quarter of an hour
- The "Fifteen" is a famous puzzle similar to the Rubik's Cube
- 15 is the number of days in the Roman "Ides" (March, May, July, October)