21020443021 has 2 divisors, whose sum is σ = 21020443022. Its totient is φ = 21020443020.

The previous prime is 21020442991. The next prime is 21020443091. The reversal of 21020443021 is 12034402012.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20949378121 + 71064900 = 144739^2 + 8430^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21020443021 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21020443021.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21020443091) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10510221510 + 10510221511.

It is an arithmetic number, because the mean of its divisors is an integer number (10510221511).

Almost surely, 2^21020443021 is an apocalyptic number.

It is an amenable number.

21020443021 is a deficient number, since it is larger than the sum of its proper divisors (1).

21020443021 is an equidigital number, since it uses as much as digits as its factorization.

21020443021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 384, while the sum is 19.

Adding to 21020443021 its reverse (12034402012), we get a palindrome (33054845033).

The spelling of 21020443021 in words is "twenty-one billion, twenty million, four hundred forty-three thousand, twenty-one".