81265943841781 has 2 divisors, whose sum is σ = 81265943841782. Its totient is φ = 81265943841780.

The previous prime is 81265943841763. The next prime is 81265943841821. The reversal of 81265943841781 is 18714834956218.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 54547692980881 + 26718250860900 = 7385641^2 + 5168970^2 .

It is a cyclic number.

It is not a de Polignac number, because 81265943841781 - 2¹³ = 81265943833589 is a prime.

It is a super-3 number, since 3×81265943841781³ (a number of 43 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81265943841881) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40632971920890 + 40632971920891.

It is an arithmetic number, because the mean of its divisors is an integer number (40632971920891).

Almost surely, 2^{81265943841781} is an apocalyptic number.

It is an amenable number.

81265943841781 is a deficient number, since it is larger than the sum of its proper divisors (1).

81265943841781 is an equidigital number, since it uses as much as digits as its factorization.

81265943841781 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 92897280, while the sum is 67.

The spelling of 81265943841781 in words is "eighty-one trillion, two hundred sixty-five billion, nine hundred forty-three million, eight hundred forty-one thousand, seven hundred eighty-one".