81851 has 8 divisors (see below), whose sum is σ = 102144. Its totient is φ = 63720.

The previous prime is 81847. The next prime is 81853. The reversal of 81851 is 15818.

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

It is a cyclic number.

It is not a de Polignac number, because 81851 - 2² = 81847 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81853) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 455 + ... + 608.

It is an arithmetic number, because the mean of its divisors is an integer number (12768).

2⁸¹⁸⁵¹ is an apocalyptic number.

81851 is a deficient number, since it is larger than the sum of its proper divisors (20293).

81851 is a wasteful number, since it uses less digits than its factorization.

81851 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1081.

The product of its digits is 320, while the sum is 23.

The square root of 81851 is about 286.0961376880. The cubic root of 81851 is about 43.4184847675.

The spelling of 81851 in words is "eighty-one thousand, eight hundred fifty-one".