81805171 has 4 divisors (see below), whose sum is σ = 93491632. Its totient is φ = 70118712.

The previous prime is 81805133. The next prime is 81805189. The reversal of 81805171 is 17150818.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 17150818 = 2 ⋅8575409.

It is a cyclic number.

It is not a de Polignac number, because 81805171 - 2²⁵ = 48250739 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81805121) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 5843220 + ... + 5843233.

It is an arithmetic number, because the mean of its divisors is an integer number (23372908).

Almost surely, 2^81805171 is an apocalyptic number.

81805171 is a deficient number, since it is larger than the sum of its proper divisors (11686461).

81805171 is a wasteful number, since it uses less digits than its factorization.

81805171 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11686460.

The product of its (nonzero) digits is 2240, while the sum is 31.

The square root of 81805171 is about 9044.6211087032. The cubic root of 81805171 is about 434.1037980758.

Adding to 81805171 its reverse (17150818), we get a palindrome (98955989).

The spelling of 81805171 in words is "eighty-one million, eight hundred five thousand, one hundred seventy-one".