21313116581 has 2 divisors, whose sum is σ = 21313116582. Its totient is φ = 21313116580.

The previous prime is 21313116523. The next prime is 21313116613. The reversal of 21313116581 is 18561131312.

It is an a-pointer prime, because the next prime (21313116613) can be obtained adding 21313116581 to its sum of digits (32).

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21313080100 + 36481 = 145990^2 + 191^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21313116581 is a prime.

It is a super-2 number, since 2×21313116581² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21313118581) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10656558290 + 10656558291.

It is an arithmetic number, because the mean of its divisors is an integer number (10656558291).

Almost surely, 2^21313116581 is an apocalyptic number.

It is an amenable number.

21313116581 is a deficient number, since it is larger than the sum of its proper divisors (1).

21313116581 is an equidigital number, since it uses as much as digits as its factorization.

21313116581 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 4320, while the sum is 32.

Adding to 21313116581 its reverse (18561131312), we get a palindrome (39874247893).

The spelling of 21313116581 in words is "twenty-one billion, three hundred thirteen million, one hundred sixteen thousand, five hundred eighty-one".