81261560041591 has 2 divisors, whose sum is σ = 81261560041592. Its totient is φ = 81261560041590.

The previous prime is 81261560041553. The next prime is 81261560041603. The reversal of 81261560041591 is 19514006516218.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 81261560041591 - 2¹⁷ = 81261559910519 is a prime.

It is a super-2 number, since 2×81261560041591² (a number of 29 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81261560045591) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40630780020795 + 40630780020796.

It is an arithmetic number, because the mean of its divisors is an integer number (40630780020796).

Almost surely, 2^{81261560041591} is an apocalyptic number.

81261560041591 is a deficient number, since it is larger than the sum of its proper divisors (1).

81261560041591 is an equidigital number, since it uses as much as digits as its factorization.

81261560041591 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 518400, while the sum is 49.

The spelling of 81261560041591 in words is "eighty-one trillion, two hundred sixty-one billion, five hundred sixty million, forty-one thousand, five hundred ninety-one".