81771870128393 has 2 divisors, whose sum is σ = 81771870128394. Its totient is φ = 81771870128392.

The previous prime is 81771870128321. The next prime is 81771870128449. The reversal of 81771870128393 is 39382107817718.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 44171083853689 + 37600786274704 = 6646133^2 + 6131948^2 .

It is a cyclic number.

It is not a de Polignac number, because 81771870128393 - 2¹² = 81771870124297 is a prime.

It is not a weakly prime, because it can be changed into another prime (81771870178393) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40885935064196 + 40885935064197.

It is an arithmetic number, because the mean of its divisors is an integer number (40885935064197).

Almost surely, 2^{81771870128393} is an apocalyptic number.

It is an amenable number.

81771870128393 is a deficient number, since it is larger than the sum of its proper divisors (1).

81771870128393 is an equidigital number, since it uses as much as digits as its factorization.

81771870128393 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 28449792, while the sum is 65.

The spelling of 81771870128393 in words is "eighty-one trillion, seven hundred seventy-one billion, eight hundred seventy million, one hundred twenty-eight thousand, three hundred ninety-three".