81801 has 12 divisors (see below), whose sum is σ = 120900. Its totient is φ = 53280.

The previous prime is 81799. The next prime is 81817. The reversal of 81801 is 10818.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 5625 + 76176 = 75^2 + 276^2 .

It is not a de Polignac number, because 81801 - 2¹ = 81799 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81001) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 475 + ... + 623.

It is an arithmetic number, because the mean of its divisors is an integer number (10075).

2⁸¹⁸⁰¹ is an apocalyptic number.

It is an amenable number.

81801 is a deficient number, since it is larger than the sum of its proper divisors (39099).

81801 is a wasteful number, since it uses less digits than its factorization.

81801 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 216 (or 213 counting only the distinct ones).

The product of its (nonzero) digits is 64, while the sum is 18.

The square root of 81801 is about 286.0087411252. The cubic root of 81801 is about 43.4096420067.

The spelling of 81801 in words is "eighty-one thousand, eight hundred one".