81139171 has 2 divisors, whose sum is σ = 81139172. Its totient is φ = 81139170.

The previous prime is 81139159. The next prime is 81139199. The reversal of 81139171 is 17193118.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 81139171 - 2⁷ = 81139043 is a prime.

It is not a weakly prime, because it can be changed into another prime (81139111) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40569585 + 40569586.

It is an arithmetic number, because the mean of its divisors is an integer number (40569586).

Almost surely, 2^81139171 is an apocalyptic number.

81139171 is a deficient number, since it is larger than the sum of its proper divisors (1).

81139171 is an equidigital number, since it uses as much as digits as its factorization.

81139171 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1512, while the sum is 31.

The square root of 81139171 is about 9007.7284039873. The cubic root of 81139171 is about 432.9225309299.

The spelling of 81139171 in words is "eighty-one million, one hundred thirty-nine thousand, one hundred seventy-one".