Is 21005 a prime number?

21 005 is an odd number, because it is not evenly divisible by 2.

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• What is an even 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 21 005 is about 144.931.

Thus, the square root of 21 005 is not an integer, and therefore 21 005 is not a square number.

The square of a number (here 21 005) is the result of the product of this number (21 005) by itself (i.e., 21 005 × 21 005); the square of 21 005 is sometimes called "raising 21 005 to the power 2", or "21 005 squared".

The square of 21 005 is 441 210 025 because 21 005 × 21 005 = 21 005² = 441 210 025.

As a consequence, 21 005 is the square root of 441 210 025.

21 005 is a number with 5 digits.

The multiples of 21 005 are all integers evenly divisible by 21 005, that is all numbers such that the remainder of the division by 21 005 is zero. There are infinitely many multiples of 21 005. The smallest multiples of 21 005 are:

• 0: indeed, 0 is divisible by any natural number, and it is thus a multiple of 21 005 too, since 0 × 21 005 = 0
• 21 005: indeed, 21 005 is a multiple of itself, since 21 005 is evenly divisible by 21 005 (we have 21 005 / 21 005 = 1, so the remainder of this division is indeed zero)
• 42 010: indeed, 42 010 = 21 005 × 2
• 63 015: indeed, 63 015 = 21 005 × 3
• 84 020: indeed, 84 020 = 21 005 × 4
• 105 025: indeed, 105 025 = 21 005 × 5
• etc.

• Preceding numbers: …21 003, 21 004
• Following numbers: 21 006, 21 007…

Nearest numbers from 21 005

• Preceding prime number: 21 001
• Following prime number: 21 011

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• 21 005 est-il un nombre premier ?