11931212581 has 2 divisors, whose sum is σ = 11931212582. Its totient is φ = 11931212580.

The previous prime is 11931212483. The next prime is 11931212609. The reversal of 11931212581 is 18521213911.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 11895392356 + 35820225 = 109066^2 + 5985^2 .

It is an emirp because it is prime and its reverse (18521213911) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 11931212581 - 2⁷ = 11931212453 is a prime.

It is a super-2 number, since 2×11931212581² (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 (11931215581) 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, 5965606290 + 5965606291.

It is an arithmetic number, because the mean of its divisors is an integer number (5965606291).

Almost surely, 2^11931212581 is an apocalyptic number.

It is an amenable number.

11931212581 is a deficient number, since it is larger than the sum of its proper divisors (1).

11931212581 is an equidigital number, since it uses as much as digits as its factorization.

11931212581 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 4320, while the sum is 34.

The spelling of 11931212581 in words is "eleven billion, nine hundred thirty-one million, two hundred twelve thousand, five hundred eighty-one".