81606765181 has 2 divisors, whose sum is σ = 81606765182. Its totient is φ = 81606765180.

The previous prime is 81606765169. The next prime is 81606765193. The reversal of 81606765181 is 18156760618.

It is a happy number.

It is a balanced prime because it is at equal distance from previous prime (81606765169) and next prime (81606765193).

It can be written as a sum of positive squares in only one way, i.e., 81533662681 + 73102500 = 285541^2 + 8550^2 .

It is a cyclic number.

It is not a de Polignac number, because 81606765181 - 2¹⁵ = 81606732413 is a prime.

It is a super-2 number, since 2×81606765181² (a number of 23 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81606715181) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40803382590 + 40803382591.

It is an arithmetic number, because the mean of its divisors is an integer number (40803382591).

Almost surely, 2^81606765181 is an apocalyptic number.

It is an amenable number.

81606765181 is a deficient number, since it is larger than the sum of its proper divisors (1).

81606765181 is an equidigital number, since it uses as much as digits as its factorization.

81606765181 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 483840, while the sum is 49.

The spelling of 81606765181 in words is "eighty-one billion, six hundred six million, seven hundred sixty-five thousand, one hundred eighty-one".