21243120013 has 4 divisors (see below), whose sum is σ = 21243586140. Its totient is φ = 21242653888.

The previous prime is 21243119971. The next prime is 21243120077. The reversal of 21243120013 is 31002134212.

It is a happy number.

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

It can be written as a sum of positive squares in 2 ways, for example, as 20689082569 + 554037444 = 143837^2 + 23538^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21243120013 is a prime.

It is a super-2 number, since 2×21243120013² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21243120313) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 156268 + ... + 258661.

It is an arithmetic number, because the mean of its divisors is an integer number (5310896535).

Almost surely, 2^21243120013 is an apocalyptic number.

It is an amenable number.

21243120013 is a deficient number, since it is larger than the sum of its proper divisors (466127).

21243120013 is an equidigital number, since it uses as much as digits as its factorization.

21243120013 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 466126.

The product of its (nonzero) digits is 288, while the sum is 19.

Adding to 21243120013 its reverse (31002134212), we get a palindrome (52245254225).

The spelling of 21243120013 in words is "twenty-one billion, two hundred forty-three million, one hundred twenty thousand, thirteen".