21115405331 has 2 divisors, whose sum is σ = 21115405332. Its totient is φ = 21115405330.

The previous prime is 21115405313. The next prime is 21115405357. The reversal of 21115405331 is 13350451112.

Together with previous prime (21115405313) it forms an Ormiston pair, because they use the same digits, order apart.

It is an a-pointer prime, because the next prime (21115405357) can be obtained adding 21115405331 to its sum of digits (26).

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21115405331 - 2¹⁰ = 21115404307 is a prime.

It is a super-2 number, since 2×21115405331² (a number of 21 digits) contains 22 as substring.

It is a Sophie Germain prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21115405331.

It is not a weakly prime, because it can be changed into another prime (21115405391) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10557702665 + 10557702666.

It is an arithmetic number, because the mean of its divisors is an integer number (10557702666).

Almost surely, 2^21115405331 is an apocalyptic number.

21115405331 is a deficient number, since it is larger than the sum of its proper divisors (1).

21115405331 is an equidigital number, since it uses as much as digits as its factorization.

21115405331 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1800, while the sum is 26.

Adding to 21115405331 its reverse (13350451112), we get a palindrome (34465856443).

The spelling of 21115405331 in words is "twenty-one billion, one hundred fifteen million, four hundred five thousand, three hundred thirty-one".