81205671 has 8 divisors (see below), whose sum is σ = 108788224. Its totient is φ = 53880120.

The previous prime is 81205667. The next prime is 81205679. The reversal of 81205671 is 17650218.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 81205671 - 2² = 81205667 is a prime.

It is a super-2 number, since 2×81205671² = 13188722005120482, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81205679) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 63511 + ... + 64776.

It is an arithmetic number, because the mean of its divisors is an integer number (13598528).

Almost surely, 2^81205671 is an apocalyptic number.

81205671 is a deficient number, since it is larger than the sum of its proper divisors (27582553).

81205671 is a wasteful number, since it uses less digits than its factorization.

81205671 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 128501.

The product of its (nonzero) digits is 3360, while the sum is 30.

The square root of 81205671 is about 9011.4189226780. The cubic root of 81205671 is about 433.0407701087.

Adding to 81205671 its reverse (17650218), we get a palindrome (98855889).

The spelling of 81205671 in words is "eighty-one million, two hundred five thousand, six hundred seventy-one".