821381641 has 2 divisors, whose sum is σ = 821381642. Its totient is φ = 821381640.

The previous prime is 821381633. The next prime is 821381663. The reversal of 821381641 is 146183128.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 616777225 + 204604416 = 24835^2 + 14304^2 .

It is a cyclic number.

It is not a de Polignac number, because 821381641 - 2³ = 821381633 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 821381597 and 821381606.

It is not a weakly prime, because it can be changed into another prime (821387641) 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, 410690820 + 410690821.

It is an arithmetic number, because the mean of its divisors is an integer number (410690821).

Almost surely, 2^821381641 is an apocalyptic number.

It is an amenable number.

821381641 is a deficient number, since it is larger than the sum of its proper divisors (1).

821381641 is an equidigital number, since it uses as much as digits as its factorization.

821381641 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 9216, while the sum is 34.

The square root of 821381641 is about 28659.7564714008. The cubic root of 821381641 is about 936.5155593651.

The spelling of 821381641 in words is "eight hundred twenty-one million, three hundred eighty-one thousand, six hundred forty-one".