21343443521 has 2 divisors, whose sum is σ = 21343443522. Its totient is φ = 21343443520.

The previous prime is 21343443427. The next prime is 21343443533. The reversal of 21343443521 is 12534434312.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19618204225 + 1725239296 = 140065^2 + 41536^2 .

It is a cyclic number.

It is not a de Polignac number, because 21343443521 - 2²⁶ = 21276334657 is a prime.

It is not a weakly prime, because it can be changed into another prime (21343443221) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10671721760 + 10671721761.

It is an arithmetic number, because the mean of its divisors is an integer number (10671721761).

Almost surely, 2^21343443521 is an apocalyptic number.

It is an amenable number.

21343443521 is a deficient number, since it is larger than the sum of its proper divisors (1).

21343443521 is an equidigital number, since it uses as much as digits as its factorization.

21343443521 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 34560, while the sum is 32.

Adding to 21343443521 its reverse (12534434312), we get a palindrome (33877877833).

The spelling of 21343443521 in words is "twenty-one billion, three hundred forty-three million, four hundred forty-three thousand, five hundred twenty-one".