81586181 has 2 divisors, whose sum is σ = 81586182. Its totient is φ = 81586180.

The previous prime is 81586163. The next prime is 81586207. The reversal of 81586181 is 18168518.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 80263681 + 1322500 = 8959^2 + 1150^2 .

It is a cyclic number.

It is not a de Polignac number, because 81586181 - 2¹⁸ = 81324037 is a prime.

It is a super-2 number, since 2×81586181² = 13312609860329522, which contains 22 as substring.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81586151) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40793090 + 40793091.

It is an arithmetic number, because the mean of its divisors is an integer number (40793091).

Almost surely, 2^81586181 is an apocalyptic number.

It is an amenable number.

81586181 is a deficient number, since it is larger than the sum of its proper divisors (1).

81586181 is an equidigital number, since it uses as much as digits as its factorization.

81586181 is an evil number, because the sum of its binary digits is even.

The product of its digits is 15360, while the sum is 38.

The square root of 81586181 is about 9032.5069056160. The cubic root of 81586181 is about 433.7160909413.

The spelling of 81586181 in words is "eighty-one million, five hundred eighty-six thousand, one hundred eighty-one".