105821 has 8 divisors (see below), whose sum is σ = 113400. Its totient is φ = 98560.

The previous prime is 105817. The next prime is 105829. The reversal of 105821 is 128501.

It can be written as a sum of positive squares in 4 ways, for example, as 196 + 105625 = 14^2 + 325^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 105821 - 2² = 105817 is a prime.

It is a super-2 number, since 2×105821² = 22396168082, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 105821.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (105829) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1145 + ... + 1233.

It is an arithmetic number, because the mean of its divisors is an integer number (14175).

2¹⁰⁵⁸²¹ is an apocalyptic number.

It is an amenable number.

105821 is a deficient number, since it is larger than the sum of its proper divisors (7579).

105821 is an equidigital number, since it uses as much as digits as its factorization.

105821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 159.

The product of its (nonzero) digits is 80, while the sum is 17.

The square root of 105821 is about 325.3013987059. The cubic root of 105821 is about 47.2995802921.

The spelling of 105821 in words is "one hundred five thousand, eight hundred twenty-one".