21121311305 has 8 divisors (see below), whose sum is σ = 25761075144. Its totient is φ = 16620048000.

The previous prime is 21121311191. The next prime is 21121311307. The reversal of 21121311305 is 50311312112.

It can be written as a sum of positive squares in 4 ways, for example, as 110229001 + 21011082304 = 10499^2 + 144952^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21121311305 - 2²⁰ = 21120262729 is a prime.

It is a super-2 number, since 2×21121311305² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21121311307) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 34624796 + ... + 34625405.

It is an arithmetic number, because the mean of its divisors is an integer number (3220134393).

Almost surely, 2^21121311305 is an apocalyptic number.

It is an amenable number.

21121311305 is a deficient number, since it is larger than the sum of its proper divisors (4639763839).

21121311305 is an equidigital number, since it uses as much as digits as its factorization.

21121311305 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 69250267.

The product of its (nonzero) digits is 180, while the sum is 20.

Adding to 21121311305 its reverse (50311312112), we get a palindrome (71432623417).

The spelling of 21121311305 in words is "twenty-one billion, one hundred twenty-one million, three hundred eleven thousand, three hundred five".