Number 821 is a prime number.

A prime number is a natural number greater than 1 that is not a product of two smaller natural numbers. Therefore we consider 821 as a prime number, because:

- 821 is a natural number greater than 1,
- 821 is not a product of 2 smaller natural numbers (it can be divided only by 1 and itself)

Number of factors: 2.

List of factors/divisors: 1, 821.

Parity: 821 is an odd number.

Perfect square: no (a square number or perfect square is an integer that is the square of an integer).

Perfect number: no, because the sum of its proper divisors is 1 (perfect number is a positive integer that is equal to the sum of its proper divisors).

Number: Prime number: | 814 no | 815 no | 816 no | 817 no | 818 no | 819 no | 820 no | 821 yes | 822 no | 823 yes | 824 no | 825 no | 826 no | 827 yes | 828 no |
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