21513134321 has 4 divisors (see below), whose sum is σ = 24586439232. Its totient is φ = 18439829412.

The previous prime is 21513134311. The next prime is 21513134323. The reversal of 21513134321 is 12343131512.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21513134321 - 2²⁶ = 21446025457 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21513134323) 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, 1536652445 + ... + 1536652458.

It is an arithmetic number, because the mean of its divisors is an integer number (6146609808).

Almost surely, 2^21513134321 is an apocalyptic number.

It is an amenable number.

21513134321 is a deficient number, since it is larger than the sum of its proper divisors (3073304911).

21513134321 is an equidigital number, since it uses as much as digits as its factorization.

21513134321 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3073304910.

The product of its digits is 2160, while the sum is 26.

Adding to 21513134321 its reverse (12343131512), we get a palindrome (33856265833).

The spelling of 21513134321 in words is "twenty-one billion, five hundred thirteen million, one hundred thirty-four thousand, three hundred twenty-one".