Is 15 a prime number?

Is 15 a prime number?

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:

  1. It has more than two distinct positive divisors (1, 3, 5, 15)
  2. 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:

  1. It's the product of two consecutive primes (3 × 5)
  2. It's a triangular number (1 + 2 + 3 + 4 + 5 = 15)
  3. It's a hexagonal number and a pentatope number
  4. It's the atomic number of phosphorus (P) on the periodic table
  5. 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
  • QuinceaƱeras 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)