81289181 has 2 divisors, whose sum is σ = 81289182. Its totient is φ = 81289180.

The previous prime is 81289177. The next prime is 81289231. The reversal of 81289181 is 18198218.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 76405081 + 4884100 = 8741^2 + 2210^2 .

It is a cyclic number.

It is not a de Polignac number, because 81289181 - 2² = 81289177 is a prime.

It is a super-2 number, since 2×81289181² = 13215861895301522, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81289151) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40644590 + 40644591.

It is an arithmetic number, because the mean of its divisors is an integer number (40644591).

Almost surely, 2^81289181 is an apocalyptic number.

It is an amenable number.

81289181 is a deficient number, since it is larger than the sum of its proper divisors (1).

81289181 is an equidigital number, since it uses as much as digits as its factorization.

81289181 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 9216, while the sum is 38.

The square root of 81289181 is about 9016.0512975471. The cubic root of 81289181 is about 433.1891622299.

The spelling of 81289181 in words is "eighty-one million, two hundred eighty-nine thousand, one hundred eighty-one".