21320243243 has 4 divisors (see below), whose sum is σ = 22960261968. Its totient is φ = 19680224520.

The previous prime is 21320243239. The next prime is 21320243249. The reversal of 21320243243 is 34234202312.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21320243243 - 2² = 21320243239 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21320243249) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 820009343 + ... + 820009368.

It is an arithmetic number, because the mean of its divisors is an integer number (5740065492).

Almost surely, 2^21320243243 is an apocalyptic number.

21320243243 is a deficient number, since it is larger than the sum of its proper divisors (1640018725).

21320243243 is a wasteful number, since it uses less digits than its factorization.

21320243243 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1640018724.

The product of its (nonzero) digits is 6912, while the sum is 26.

Adding to 21320243243 its reverse (34234202312), we get a palindrome (55554445555).

The spelling of 21320243243 in words is "twenty-one billion, three hundred twenty million, two hundred forty-three thousand, two hundred forty-three".