820580921 has 2 divisors, whose sum is σ = 820580922. Its totient is φ = 820580920.

The previous prime is 820580833. The next prime is 820580923. The reversal of 820580921 is 129085028.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 786522025 + 34058896 = 28045^2 + 5836^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-820580921 is a prime.

Together with 820580923, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (820580923) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 410290460 + 410290461.

It is an arithmetic number, because the mean of its divisors is an integer number (410290461).

Almost surely, 2^820580921 is an apocalyptic number.

It is an amenable number.

820580921 is a deficient number, since it is larger than the sum of its proper divisors (1).

820580921 is an equidigital number, since it uses as much as digits as its factorization.

820580921 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 11520, while the sum is 35.

The square root of 820580921 is about 28645.7836513509. The cubic root of 820580921 is about 936.2111411718.

The spelling of 820580921 in words is "eight hundred twenty million, five hundred eighty thousand, nine hundred twenty-one".