821234579821 has 2 divisors, whose sum is σ = 821234579822. Its totient is φ = 821234579820.

The previous prime is 821234579807. The next prime is 821234579827. The reversal of 821234579821 is 128975432128.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 756571175721 + 64663404100 = 869811^2 + 254290^2 .

It is a cyclic number.

It is not a de Polignac number, because 821234579821 - 2¹⁹ = 821234055533 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (821234579827) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 410617289910 + 410617289911.

It is an arithmetic number, because the mean of its divisors is an integer number (410617289911).

Almost surely, 2^821234579821 is an apocalyptic number.

It is an amenable number.

821234579821 is a deficient number, since it is larger than the sum of its proper divisors (1).

821234579821 is an equidigital number, since it uses as much as digits as its factorization.

821234579821 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1935360, while the sum is 52.

The spelling of 821234579821 in words is "eight hundred twenty-one billion, two hundred thirty-four million, five hundred seventy-nine thousand, eight hundred twenty-one".