81505 has 4 divisors (see below), whose sum is σ = 97812. Its totient is φ = 65200.

The previous prime is 81463. The next prime is 81509. The reversal of 81505 is 50518.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 50176 + 31329 = 224^2 + 177^2 .

It is a de Polignac number, because none of the positive numbers 2^k-81505 is a prime.

It is an Ulam number.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81509) 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, 8146 + ... + 8155.

It is an arithmetic number, because the mean of its divisors is an integer number (24453).

2⁸¹⁵⁰⁵ is an apocalyptic number.

It is an amenable number.

81505 is a deficient number, since it is larger than the sum of its proper divisors (16307).

81505 is a wasteful number, since it uses less digits than its factorization.

81505 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 16306.

The product of its (nonzero) digits is 200, while the sum is 19.

The square root of 81505 is about 285.4908054561. The cubic root of 81505 is about 43.3572189159.

The spelling of 81505 in words is "eighty-one thousand, five hundred five".