821447821 has 2 divisors, whose sum is σ = 821447822. Its totient is φ = 821447820.

The previous prime is 821447813. The next prime is 821447849. The reversal of 821447821 is 128744128.

It is a happy number.

821447821 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., 608608900 + 212838921 = 24670^2 + 14589^2 .

It is a cyclic number.

It is not a de Polignac number, because 821447821 - 2³ = 821447813 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (821441821) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 410723910 + 410723911.

It is an arithmetic number, because the mean of its divisors is an integer number (410723911).

Almost surely, 2^821447821 is an apocalyptic number.

It is an amenable number.

821447821 is a deficient number, since it is larger than the sum of its proper divisors (1).

821447821 is an equidigital number, since it uses as much as digits as its factorization.

821447821 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 28672, while the sum is 37.

The square root of 821447821 is about 28660.9110287862. The cubic root of 821447821 is about 936.5407108627.

The spelling of 821447821 in words is "eight hundred twenty-one million, four hundred forty-seven thousand, eight hundred twenty-one".