21311287553 has 2 divisors, whose sum is σ = 21311287554. Its totient is φ = 21311287552.

The previous prime is 21311287523. The next prime is 21311287607. The reversal of 21311287553 is 35578211312.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 17904580864 + 3406706689 = 133808^2 + 58367^2 .

It is a cyclic number.

It is not a de Polignac number, because 21311287553 - 2¹² = 21311283457 is a prime.

It is not a weakly prime, because it can be changed into another prime (21311287523) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10655643776 + 10655643777.

It is an arithmetic number, because the mean of its divisors is an integer number (10655643777).

Almost surely, 2^21311287553 is an apocalyptic number.

It is an amenable number.

21311287553 is a deficient number, since it is larger than the sum of its proper divisors (1).

21311287553 is an equidigital number, since it uses as much as digits as its factorization.

21311287553 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 50400, while the sum is 38.

Adding to 21311287553 its reverse (35578211312), we get a palindrome (56889498865).

The spelling of 21311287553 in words is "twenty-one billion, three hundred eleven million, two hundred eighty-seven thousand, five hundred fifty-three".