21512311321 has 2 divisors, whose sum is σ = 21512311322. Its totient is φ = 21512311320.

The previous prime is 21512311319. The next prime is 21512311339. The reversal of 21512311321 is 12311321512.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 11465055625 + 10047255696 = 107075^2 + 100236^2 .

It is a cyclic number.

It is not a de Polignac number, because 21512311321 - 2¹ = 21512311319 is a prime.

Together with 21512311319, it forms a pair of twin primes.

It is a junction number, because it is equal to n+sod(n) for n = 21512311292 and 21512311301.

It is not a weakly prime, because it can be changed into another prime (21512311021) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10756155660 + 10756155661.

It is an arithmetic number, because the mean of its divisors is an integer number (10756155661).

Almost surely, 2^21512311321 is an apocalyptic number.

It is an amenable number.

21512311321 is a deficient number, since it is larger than the sum of its proper divisors (1).

21512311321 is an equidigital number, since it uses as much as digits as its factorization.

21512311321 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 360, while the sum is 22.

Adding to 21512311321 its reverse (12311321512), we get a palindrome (33823632833).

The spelling of 21512311321 in words is "twenty-one billion, five hundred twelve million, three hundred eleven thousand, three hundred twenty-one".