81481 has 4 divisors (see below), whose sum is σ = 86292. Its totient is φ = 76672.

The previous prime is 81463. The next prime is 81509. The reversal of 81481 is 18418.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 18418 = 2 ⋅9209.

It can be written as a sum of positive squares in 2 ways, for example, as 67081 + 14400 = 259^2 + 120^2 .

It is a cyclic number.

It is not a de Polignac number, because 81481 - 2⁷ = 81353 is a prime.

It is a super-2 number, since 2×81481² = 13278306722, which contains 22 as substring.

81481 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81401) 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, 2380 + ... + 2413.

It is an arithmetic number, because the mean of its divisors is an integer number (21573).

2⁸¹⁴⁸¹ is an apocalyptic number.

It is an amenable number.

81481 is a deficient number, since it is larger than the sum of its proper divisors (4811).

81481 is a wasteful number, since it uses less digits than its factorization.

81481 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4810.

The product of its digits is 256, while the sum is 22.

The square root of 81481 is about 285.4487694841. The cubic root of 81481 is about 43.3529628358.

Subtracting from 81481 its product of digits (256), we obtain a square (81225 = 285²).

Adding to 81481 its reverse (18418), we get a palindrome (99899).

The spelling of 81481 in words is "eighty-one thousand, four hundred eighty-one".