21843006821 has 2 divisors, whose sum is σ = 21843006822. Its totient is φ = 21843006820.

The previous prime is 21843006817. The next prime is 21843006833. The reversal of 21843006821 is 12860034812.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 12202516225 + 9640490596 = 110465^2 + 98186^2 .

It is a cyclic number.

It is not a de Polignac number, because 21843006821 - 2² = 21843006817 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21843006881) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10921503410 + 10921503411.

It is an arithmetic number, because the mean of its divisors is an integer number (10921503411).

Almost surely, 2^21843006821 is an apocalyptic number.

It is an amenable number.

21843006821 is a deficient number, since it is larger than the sum of its proper divisors (1).

21843006821 is an equidigital number, since it uses as much as digits as its factorization.

21843006821 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 18432, while the sum is 35.

The spelling of 21843006821 in words is "twenty-one billion, eight hundred forty-three million, six thousand, eight hundred twenty-one".