15812149781581 has 2 divisors, whose sum is σ = 15812149781582. Its totient is φ = 15812149781580.

The previous prime is 15812149781453. The next prime is 15812149781609. The reversal of 15812149781581 is 18518794121851.

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., 15805037558025 + 7112223556 = 3975555^2 + 84334^2 .

It is a cyclic number.

It is not a de Polignac number, because 15812149781581 - 2⁷ = 15812149781453 is a prime.

It is a super-2 number, since 2×15812149781581² (a number of 27 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (15812149751581) 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, 7906074890790 + 7906074890791.

It is an arithmetic number, because the mean of its divisors is an integer number (7906074890791).

Almost surely, 2^{15812149781581} is an apocalyptic number.

It is an amenable number.

15812149781581 is a deficient number, since it is larger than the sum of its proper divisors (1).

15812149781581 is an equidigital number, since it uses as much as digits as its factorization.

15812149781581 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 6451200, while the sum is 61.

The spelling of 15812149781581 in words is "fifteen trillion, eight hundred twelve billion, one hundred forty-nine million, seven hundred eighty-one thousand, five hundred eighty-one".