820539721 has 2 divisors, whose sum is σ = 820539722. Its totient is φ = 820539720.

The previous prime is 820539703. The next prime is 820539737. The reversal of 820539721 is 127935028.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 533610000 + 286929721 = 23100^2 + 16939^2 .

It is a cyclic number.

It is not a de Polignac number, because 820539721 - 2⁷ = 820539593 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (820539521) 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, 410269860 + 410269861.

It is an arithmetic number, because the mean of its divisors is an integer number (410269861).

Almost surely, 2^820539721 is an apocalyptic number.

It is an amenable number.

820539721 is a deficient number, since it is larger than the sum of its proper divisors (1).

820539721 is an equidigital number, since it uses as much as digits as its factorization.

820539721 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 30240, while the sum is 37.

The square root of 820539721 is about 28645.0645138041. The cubic root of 820539721 is about 936.1954723761.

The spelling of 820539721 in words is "eight hundred twenty million, five hundred thirty-nine thousand, seven hundred twenty-one".