21243443121 has 6 divisors (see below), whose sum is σ = 30684973410. Its totient is φ = 14162295408.

The previous prime is 21243443113. The next prime is 21243443131. The reversal of 21243443121 is 12134434212.

21243443121 is a `hidden beast` number, since 2 + 1 + 2 + 4 + 344 + 312 + 1 = 666.

It can be written as a sum of positive squares in only one way, i.e., 13759290000 + 7484153121 = 117300^2 + 86511^2 .

It is not a de Polignac number, because 21243443121 - 2³ = 21243443113 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21243443131) 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 in 5 ways as a sum of consecutive naturals, for example, 1180191276 + ... + 1180191293.

It is an arithmetic number, because the mean of its divisors is an integer number (5114162235).

Almost surely, 2^21243443121 is an apocalyptic number.

It is an amenable number.

21243443121 is a deficient number, since it is larger than the sum of its proper divisors (9441530289).

21243443121 is a wasteful number, since it uses less digits than its factorization.

21243443121 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2360382575 (or 2360382572 counting only the distinct ones).

The product of its digits is 4608, while the sum is 27.

Adding to 21243443121 its reverse (12134434212), we get a palindrome (33377877333).

The spelling of 21243443121 in words is "twenty-one billion, two hundred forty-three million, four hundred forty-three thousand, one hundred twenty-one".