81131081 has 2 divisors, whose sum is σ = 81131082. Its totient is φ = 81131080.

The previous prime is 81131041. The next prime is 81131093. The reversal of 81131081 is 18013118.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 68740681 + 12390400 = 8291^2 + 3520^2 .

It is a cyclic number.

It is not a de Polignac number, because 81131081 - 2¹⁴ = 81114697 is a prime.

It is a super-2 number, since 2×81131081² = 13164504608457122, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (81131041) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40565540 + 40565541.

It is an arithmetic number, because the mean of its divisors is an integer number (40565541).

Almost surely, 2^81131081 is an apocalyptic number.

It is an amenable number.

81131081 is a deficient number, since it is larger than the sum of its proper divisors (1).

81131081 is an equidigital number, since it uses as much as digits as its factorization.

81131081 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 192, while the sum is 23.

The square root of 81131081 is about 9007.2793339609. The cubic root of 81131081 is about 432.9081422377.

Adding to 81131081 its reverse (18013118), we get a palindrome (99144199).

The spelling of 81131081 in words is "eighty-one million, one hundred thirty-one thousand, eighty-one".