820909 has 2 divisors, whose sum is σ = 820910. Its totient is φ = 820908.

The previous prime is 820907. The next prime is 820921. The reversal of 820909 is 909028.

It is a happy number.

820909 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 756900 + 64009 = 870^2 + 253^2 .

It is a cyclic number.

It is not a de Polignac number, because 820909 - 2¹ = 820907 is a prime.

Together with 820907, it forms a pair of twin primes.

820909 is a modest number, since divided by 909 gives 82 as remainder.

It is equal to p₆₅₄₈₅ and since 820909 and 65485 have the same sum of digits, it is a Honaker prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (820901) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 410454 + 410455.

It is an arithmetic number, because the mean of its divisors is an integer number (410455).

2⁸²⁰⁹⁰⁹ is an apocalyptic number.

It is an amenable number.

820909 is a deficient number, since it is larger than the sum of its proper divisors (1).

820909 is an equidigital number, since it uses as much as digits as its factorization.

820909 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1296, while the sum is 28.

The square root of 820909 is about 906.0402860800. The cubic root of 820909 is about 93.6335894373.

The spelling of 820909 in words is "eight hundred twenty thousand, nine hundred nine".