81723 has 4 divisors (see below), whose sum is σ = 108968. Its totient is φ = 54480.

The previous prime is 81707. The next prime is 81727. The reversal of 81723 is 32718.

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

It is not a de Polignac number, because 81723 - 2⁴ = 81707 is a prime.

It is a D-number.

It is a Duffinian number.

81723 is a lucky number.

It is a self number, because there is not a number n which added to its sum of digits gives 81723.

It is not an unprimeable number, because it can be changed into a prime (81727) 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, 13618 + ... + 13623.

It is an arithmetic number, because the mean of its divisors is an integer number (27242).

2⁸¹⁷²³ is an apocalyptic number.

81723 is a deficient number, since it is larger than the sum of its proper divisors (27245).

81723 is a wasteful number, since it uses less digits than its factorization.

81723 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 27244.

The product of its digits is 336, while the sum is 21.

The square root of 81723 is about 285.8723491351. The cubic root of 81723 is about 43.3958401019.

The spelling of 81723 in words is "eighty-one thousand, seven hundred twenty-three".