Is 505 a prime number?

It is possible to find out using mathematical methods whether a given integer is a prime number or not.

For 505, the answer is: No, 505 is not a prime number.

The list of all positive divisors (i.e., the list of all integers that divide 505) is as follows: 1, 5, 101, 505.

For 505 to be a prime number, it would have been required that 505 has only two divisors, i.e., itself and 1.

Find out more:

What is a prime number?

Actually, one can immediately see that 505 cannot be prime, because 5 is one of its divisors: indeed, a number ending with 0 or 5 has necessarily 5 among its divisors. The last digit of 505 is 5, so it is divisible by 5 and is therefore not prime.

As a consequence:

505 is a multiple of 1
505 is a multiple of 5
505 is a multiple of 101

For 505 to be a prime number, it would have been required that 505 has only two divisors, i.e., itself and 1.

However, 505 is a semiprime (also called biprime or 2-almost-prime), because it is the product of a two non-necessarily distinct prime numbers. Indeed, 505 = 5 x 101, where 5 and 101 are both prime numbers.

Is 505 a deficient number?

Yes, 505 is a deficient number, that is to say 505 is a natural number that is strictly larger than the sum of its proper divisors, i.e., the divisors of 505 without 505 itself (that is 1 + 5 + 101 = 107).

Parity of 505

505 is an odd number, because it is not evenly divisible by 2.

Find out more:

What is an even number?

Is 505 a perfect square number?

A number is a perfect square (or a square number) if its square root is an integer; that is to say, it is the product of an integer with itself. Here, the square root of 505 is about 22.472.

Thus, the square root of 505 is not an integer, and therefore 505 is not a square number.

What is the square number of 505?

The square of a number (here 505) is the result of the product of this number (505) by itself (i.e., 505 × 505); the square of 505 is sometimes called "raising 505 to the power 2", or "505 squared".

The square of 505 is 255 025 because 505 × 505 = 505² = 255 025.

As a consequence, 505 is the square root of 255 025.

Number of digits of 505

505 is a number with 3 digits.

What are the multiples of 505?

The multiples of 505 are all integers evenly divisible by 505, that is all numbers such that the remainder of the division by 505 is zero. There are infinitely many multiples of 505. The smallest multiples of 505 are:

0: indeed, 0 is divisible by any natural number, and it is thus a multiple of 505 too, since 0 × 505 = 0
505: indeed, 505 is a multiple of itself, since 505 is evenly divisible by 505 (we have 505 / 505 = 1, so the remainder of this division is indeed zero)
1 010: indeed, 1 010 = 505 × 2
1 515: indeed, 1 515 = 505 × 3
2 020: indeed, 2 020 = 505 × 4
2 525: indeed, 2 525 = 505 × 5
etc.

How to determine whether an integer is a prime number?

To determine the primality of a number, several algorithms can be used. The most naive technique is to test all divisors strictly smaller to the number of which we want to determine the primality (here 505). First, we can eliminate all even numbers greater than 2 (and hence 4, 6, 8…). Then, we can stop this check when we reach the square root of the number of which we want to determine the primality (here the square root is about 22.472). Historically, the sieve of Eratosthenes (dating from the Greek mathematics) implements this technique in a relatively efficient manner.

More modern techniques include the sieve of Atkin, probabilistic algorithms, and the cyclotomic AKS test.

Numbers near 505

Preceding numbers: …503, 504
Following numbers: 506, 507…

Nearest numbers from 505

Preceding prime number: 503
Following prime number: 509