821020220821 has 2 divisors, whose sum is σ = 821020220822. Its totient is φ = 821020220820.

The previous prime is 821020220723. The next prime is 821020220861. The reversal of 821020220821 is 128022020128.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 511983180900 + 309037039921 = 715530^2 + 555911^2 .

It is a cyclic number.

It is not a de Polignac number, because 821020220821 - 2²¹ = 821018123669 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 821020220821.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (821020220861) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 410510110410 + 410510110411.

It is an arithmetic number, because the mean of its divisors is an integer number (410510110411).

Almost surely, 2^821020220821 is an apocalyptic number.

It is an amenable number.

821020220821 is a deficient number, since it is larger than the sum of its proper divisors (1).

821020220821 is an equidigital number, since it uses as much as digits as its factorization.

821020220821 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 2048, while the sum is 28.

Adding to 821020220821 its reverse (128022020128), we get a palindrome (949042240949).

The spelling of 821020220821 in words is "eight hundred twenty-one billion, twenty million, two hundred twenty thousand, eight hundred twenty-one".