820978421 has 2 divisors, whose sum is σ = 820978422. Its totient is φ = 820978420.

The previous prime is 820978397. The next prime is 820978447. The reversal of 820978421 is 124879028.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 711022225 + 109956196 = 26665^2 + 10486^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-820978421 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (820978121) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 410489210 + 410489211.

It is an arithmetic number, because the mean of its divisors is an integer number (410489211).

Almost surely, 2^820978421 is an apocalyptic number.

It is an amenable number.

820978421 is a deficient number, since it is larger than the sum of its proper divisors (1).

820978421 is an equidigital number, since it uses as much as digits as its factorization.

820978421 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 64512, while the sum is 41.

The square root of 820978421 is about 28652.7210051681. The cubic root of 820978421 is about 936.3622876929.

The spelling of 820978421 in words is "eight hundred twenty million, nine hundred seventy-eight thousand, four hundred twenty-one".