81813571 has 16 divisors (see below), whose sum is σ = 99477504. Its totient is φ = 65683584.

The previous prime is 81813551. The next prime is 81813577. The reversal of 81813571 is 17531818.

It is a cyclic number.

It is not a de Polignac number, because 81813571 - 2¹³ = 81805379 is a prime.

It is not an unprimeable number, because it can be changed into a prime (81813577) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 24996 + ... + 28078.

It is an arithmetic number, because the mean of its divisors is an integer number (6217344).

Almost surely, 2^81813571 is an apocalyptic number.

81813571 is a deficient number, since it is larger than the sum of its proper divisors (17663933).

81813571 is a wasteful number, since it uses less digits than its factorization.

81813571 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3330.

The product of its digits is 6720, while the sum is 34.

The square root of 81813571 is about 9045.0854611772. The cubic root of 81813571 is about 434.1186559267.

The spelling of 81813571 in words is "eighty-one million, eight hundred thirteen thousand, five hundred seventy-one".