85721 has 4 divisors (see below), whose sum is σ = 89472. Its totient is φ = 81972.

The previous prime is 85717. The next prime is 85733. The reversal of 85721 is 12758.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 12758 = 2 ⋅6379.

It is not a de Polignac number, because 85721 - 2² = 85717 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (23), and also a Moran number because the ratio is a prime number: 3727 = 85721 / (8 + 5 + 7 + 2 + 1).

It is a Duffinian number.

It is a plaindrome in base 14.

It is not an unprimeable number, because it can be changed into a prime (85711) 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, 1841 + ... + 1886.

It is an arithmetic number, because the mean of its divisors is an integer number (22368).

2⁸⁵⁷²¹ is an apocalyptic number.

It is an amenable number.

85721 is a deficient number, since it is larger than the sum of its proper divisors (3751).

85721 is a wasteful number, since it uses less digits than its factorization.

85721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3750.

The product of its digits is 560, while the sum is 23.

The square root of 85721 is about 292.7814884859. The cubic root of 85721 is about 44.0922650687.

It can be divided in two parts, 857 and 21, that added together give a palindrome (878).

The spelling of 85721 in words is "eighty-five thousand, seven hundred twenty-one".