21013340208961 has 3 divisors (see below), whose sum is σ = 21013344792993. Its totient is φ = 21013335624930.

The previous prime is 21013340208901. The next prime is 21013340209039. The reversal of 21013340208961 is 16980204331012.

It is a happy number.

The square root of 21013340208961 is 4584031.

It is a perfect power (a square), and thus also a powerful number.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is not a de Polignac number, because 21013340208961 - 2²⁷ = 21013205991233 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21013340208901) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 2 ways as a sum of consecutive naturals, for example, 2292016 + ... + 6876046.

It is an arithmetic number, because the mean of its divisors is an integer number (7004448264331).

Almost surely, 2^{21013340208961} is an apocalyptic number.

21013340208961 is the 4584031-st square number.

21013340208961 is the 2292016-th centered octagonal number.

It is an amenable number.

21013340208961 is a deficient number, since it is larger than the sum of its proper divisors (4584032).

21013340208961 is an frugal number, since it uses more digits than its factorization.

21013340208961 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9168062 (or 4584031 counting only the distinct ones).

The product of its (nonzero) digits is 62208, while the sum is 40.

Adding to 21013340208961 its reverse (16980204331012), we get a palindrome (37993544539973).

The spelling of 21013340208961 in words is "twenty-one trillion, thirteen billion, three hundred forty million, two hundred eight thousand, nine hundred sixty-one".