65821 has 4 divisors (see below), whose sum is σ = 75232. Its totient is φ = 56412.

The previous prime is 65809. The next prime is 65827. The reversal of 65821 is 12856.

It is a happy number.

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.

It is a cyclic number.

It is not a de Polignac number, because 65821 - 2⁵ = 65789 is a prime.

It is a Duffinian number.

It is a nialpdrome in base 12.

It is a junction number, because it is equal to n+sod(n) for n = 65792 and 65801.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (65827) 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, 4695 + ... + 4708.

It is an arithmetic number, because the mean of its divisors is an integer number (18808).

2⁶⁵⁸²¹ is an apocalyptic number.

It is an amenable number.

65821 is a deficient number, since it is larger than the sum of its proper divisors (9411).

65821 is an equidigital number, since it uses as much as digits as its factorization.

65821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9410.

The product of its digits is 480, while the sum is 22.

The square root of 65821 is about 256.5560367639. The cubic root of 65821 is about 40.3758326851.

Subtracting from 65821 its product of digits (480), we obtain a triangular number (65341 = T₃₆₁).

The spelling of 65821 in words is "sixty-five thousand, eight hundred twenty-one".